The United States could make a decision as early as this week on whether to arm Syrian rebels, U.S. officials said on Monday, as U.S. Secretary of State John Kerry put off a Middle East trip to attend meetings on the subject.

However, the U.S. government has debated for months whether to provide weaponry to the rebels in their civil war against Syrian President Bashar al-Assad's forces and has so far decided against.

One U.S. official who spoke on condition of anonymity stressed that while a decision on whether to start arming the rebels is possible as soon as this week, deliberations on the issue could easily take longer.

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A look back at the conflict that has overtaken the country.

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Kerry put off a planned trip to Israel and the Palestinian territories to attend the White House meetings, an Obama administration source said.

What has changed in recent weeks is the tilting of the battlefield against the rebels as Lebanese Hezbollah has entered the fray on the side of Assad's forces, helping them to retake the strategic town of Qusair. .

That shift has made it less likely that a U.S. and Russian planned peace conference to bring the rebels and the government to the table would succeed in U.S. President Barack Obama's aim of a negotiated political transition to remove Assad from power.

Meanwhile, Israel's intelligence minister repeated a warning that Assad could prevail in the civil war because of backing from Iran and Lebanon's Hezbollah.

Yuval Steinitz, minister for international affairs, strategy and intelligence, was asked at a briefing with foreign journalists Monday whether recent successes by Assad's forces against outgunned rebels might herald victory for the Syrian leader.

"I always thought that it might be the case that at the end of the day Assad, with a very strong Iranian and Hezbollah backing, might gain the upper hand," Steinitz said. "And I think that this is possible and I thought that this is possible already a long time ago."

Steinitz, who is not a member of Israel's security cabinet but does have access to intelligence updates as well as Netanyahu's ear, said Assad's government "might not just survive but even regain territories" from the rebels.

BEIRUT -- An unarmed Lebanese protester was killed on Sunday by gunfire in front of the Iranian Embassy in Beirut, Lebanese security officials said.

It was not clear who killed the man, a member of a small crowd demonstrating against the backing of Iran and its Hezbollah ally for Syrian President Bashar Assad.

Pro-Assad Lebanese gunmen were in the vicinity at the time of the killing, the sources said.

This is a breaking news story. Please check back for updates.

Al-Manar TV via Reuters

A man carrying a Syrian flag with an image of President Bashar Assad on it looks down from a clock tower in Qusair after the Syrian army took control of the city from rebel fighters in this still image taken from video, on Wednesday.

A young soldier clambered to the top of a badly damaged clock tower in the battered Syrian city of Qusair and planted the regime flag for all the world to see. In case there was any doubt as to his political leanings, he glued President Bashar Assad's smiling face onto the banner. Subtlety – like all good things in times of war – is easily sacrificed.

There is no question that the fall of Qusair to Assad's forces is a major blow to rebels hoping to bring down the regime. This small western town straddles one of the major highways that link the capital Damascus to the Alawite strongholds on the Mediterranean coast. It is from these Alawite communities that Assad -- an Alawite (a sect of Shi'ite Islam) himself -- derives most of his power.

More crucially for the rebels, the loss of Qusair means the loss of a major supply line into central Syria. The opposition in that specific area relied heavily on the Sunni community in neighboring Lebanon for arms and medical aid, so without Qusair their access to Lebanon will be severely handicapped.

Should the Syrian regime manage to seal off the Lebanese border completely, then all the arms shipments and aid that accompanies them will dry up.

However, as significant as this battle is for Assad, the victory in Qusair does not necessarily mean the civil war is anywhere near its end.

The rebels still hold large swaths of the country – especially in the north, where they are better equipped than their fellow fighters in Qusair.

Their lines of support are also much stronger. Northern Syria runs along the Turkish border for hundreds of miles and the Turkish government has openly supported the rebels with arms, supplies and all the available logistical back-up they need. This level of backing, as well as increased arms supplies from Arab states like Qatar and Saudi Arabia, is not likely to evaporate.

Additionally, the European Union has lifted its self-imposed ban on supplying the rebels with arms. The events of the last few days may concentrate their minds further and speed up the supplies to the opposition.

This war has claimed over 80,000 lives in almost two years. The number of injured is many times more. No regime, however coercive, can quell such a rebellion. Qusair was a major morale boost for the Syrian regime but Assad and his army should not forget that it took weeks of heavy fighting and the intervention of thousands of Hezbollah fighters to dislodge the rebels from the town.

The victory was hardly a cakewalk and other battles will most likely be even harder to win.

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A look back at the conflict that has overtaken the country.

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• UN launches 'largest humanitarian appeal in history' for Syria
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• How a line drawn in the sand nearly 100 years ago helped create Syria mess
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Wael Hamzeh / EPA, file

A wounded man awaits medical attention after two rockets allegedly launched by Syrian rebels hit houses and cars in a southern suburb of Beirut, Lebanon on May 26, 2013.

News Analysis

BEIRUT, Lebanon – Syria’s civil war is beginning to spill over to its neighbors – beyond the flood of hundreds of thousands of refugees fleeing the crisis.

In a rise in sectarian violence, Sunni rebels from Syria have begun to clash with Shiite Lebanese Hezbollah fighters inside Lebanon. And the rebels have threatened more cross-border attacks unless Hezbollah ceases to defend the Alawite regime of President Bashar Assad, itself an offshoot of Shiite Islam. 

But that very border is just one of many drawn 97 years ago by a finger passing over a map ... and a line in the sand.

Now, there’s an almost amusing irony in the fact that Britain and France are the countries leading the charge to take on Assad and clean up Syria’s mess – since one could strongly argue that they are the very same colonial powers who made the mess in the first place.

“They created the contemporary Arab world,” explained Dr. Fawaz Gerges, director of the Middle East Center at the London School of Economics. “They played God and produced mutilated entities that almost a century later are coming apart.”

A line in the sand
Like so many other Middle Eastern conflicts, Syria’s war has its roots in the colonial era and dates back to World War I. By 1916 it looked doubtful that Turkey, the head of the Ottoman Empire, which was fighting with Germany and Austria, would end up on the winning side of World War I.

U.K. National Archives

A map of the Middle East with annotations showing proposed administration, including British (B) and French (A) spheres of influence, independent Arab States, and the 'Sykes-Picot Line'. Signed: Sir Mark Sykes and Fr[ançois] Georges-Picot, 8 May 1916.

So a young, keen British politician named Sir Mark Sykes was tasked by the war council to devise a secret plan that would effectively divvy up the Ottoman lands in the Middle East between Britain and France. Sykes, along with his equally driven French counterpart, the former consul in Beirut, Francois George-Picot, came up with perhaps the most fateful diagonal line ever drawn on a map. 

According to the Sykes-Picot plan, Britain got Jordan, parts of Palestine and Mesopotamia (modern-day Iraq). 

Sykes clearly wanted to keep this simple. As James Barr recounts in his recent book, “Line in the Sand,” when Skyes was asked by then-British Foreign Secretary Lord Balfour, “What do you mean to give [the French] exactly?” Sykes “sliced his finger across the map that lay before them on the table. ‘I should like to draw a line from the ‘e’ in Acre to the last ‘k’ in Kirkuk,’ he said.”

In other words, France would get part of Turkey, Syria and what became modern-day Lebanon.

Keystone-france / Gamma-Keystone via Getty Images

French soldiers entering Beirut, Lebanon, in 1919. Just after the First World War the Ottoman Empire, allies of the Germans, was dissolved. Following the 1916 Sykes-Picot agreement, Lebanon was placed under French mandate by the League of Nations in 1920.

Several years later, the League of Nations – precursor to the United Nations – cemented the new boundaries drawn up by Sykes and Picot. Boundaries which, as journalist and author Sam Roberts has written in the New York Times, “paid little attention to the ancient tribal, ethnic, and religious differences that are at the root of much of the bloodshed in the region.”

A deliberate hodge-podge 
Both colonial Britain and France, according to Roberts, were more interested in access to Middle East oil, and keeping emerging nations like Iraq and Syria divided and as weak as possible, so as not to pose a threat.

Lebanon, for instance, was carved out of Syria’s coastal region. Sunnis, Shiites, Christians and Druze were separated by geography and from their own sects in neighboring countries. Kurds found themselves spread across four countries -- Turkey, Iraq, Iran and Syria. The map of Iraq looked more like a layer cake, stacking up three former Ottoman provinces: mostly Sunni Baghdad, Shiite Basra and Kurdish Mosul.

To rule over such a hodge-podge, secular and Western-friendly kings were put onto invented thrones. Faisal bin Hussein, who fought alongside the legendary T.E. Lawrence (of Arabia) against the Turks in WWI was named king of the new Iraq; his brother, Abdullah bin Hussein, the king of the new Jordan. They both came from Saudi Arabia. Rump Syria became a French protectorate.

It was a formula, though, which seemed to work ... until post-colonial times, in the 1930s and ‘40s, when both Britain and France – having locked up their riches – granted independence to their Middle Eastern colonies. Republics replaced kings, and soon a string of military coups followed. So did dictators – some supported by the U.S. – along with ethnic cleansing and sectarian repression.

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A look back at the conflict that has overtaken the country.

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And that leads to the mess we have today, where a conflict inside one Middle Eastern country (Syria) seems to suck in another (Lebanon, Iraq). Still, Gerges, the academic, is optimistic.

“What we’ve witnessed in the past two years are birth pangs. It’ll take time and pain for a new world to replace the colonial constructed map. But it will be born.”

Jim Maceda is an NBC News foreign correspondent based in London currently on assignment in Beirut. He has covered the Middle East since the 1980’s.

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BEIRUT -- Syrian troops and Hezbollah guerrillas besieging the border town of Qusair fought with rebels on Saturday as the United Nations warned all sides they would be held accountable for the suffering of trapped civilians. 

The Britain-based Syrian Observatory for Human Rights said fighting was taking place inside Qusair and in villages around it, largely controlled by President Bashar al-Assad's forces who have cut off access to the town. 

Rebels have pleaded for military help and medical aid for the hundreds of people wounded in the onslaught by government forces, who are also fighting back fiercely around the capital Damascus and the south and center of the country. 

The battle for Qusair is happening as the United States and Russia seek to overcome deep differences over Syria and bring the two sides to the negotiating table for a political solution to the civil war in which 80,000 people have been killed. 

United Nations Secretary-General Ban Ki-moon was monitoring the battle for Qusair "with the gravest concern" and called on both sides to allow civilians to escape the town, usually home to 30,000 people. 

"The eyes of the world are upon them, and ... they will be held accountable for any acts of atrocity carried out against the civilian population of Qusair," a U.N. statement said. 

U.N. emergency relief coordinator Valerie Amos and High Commissioner for Human Rights Navi Pillay said they were alarmed that thousands of civilians may be trapped in Qusair. 

"We understand there may also be as many as 1,500 wounded people in urgent need of immediate evacuation for emergency medical treatment, and that the general situation in Qusair is desperate," they said in a joint statement. 

The Observatory, an anti-Assad network that monitors the violence in Syria through medical and security sources on the ground, said at least one person was killed during fighting inside Qusair and that Assad's troops were being reinforced ahead of a possible assault on the remaining rebel-held areas. 

Rebels also tried to attack the nearby Daba military air base, seized by the army on Wednesday, and fought Assad's troops around Daba village, it said. 

The two-week battle for Qusair is aimed at securing supply routes near the Syrian-Lebanese frontier, which both sides accuse the other of using to bolster their forces inside Syria. 

For Assad, seizing Qusair would also allow him to cement control of a belt of territory between the capital Damascus and his stronghold on the Mediterranean coast. 

The prominent role of guerrillas from Lebanon's Shi'ite group Hezbollah has angered rebels, who have threatened to take the battle into Lebanon unless Hezbollah withdraws. 

Early on Saturday at least seven rockets were fired into Lebanon's eastern Bekaa Valley from rebel-controlled Syrian territory, security sources said. 

Most of the rockets landed in empty fields. No one was hurt but some buildings were hit by shrapnel. 

It was the first time the area, about 35 miles east of Beirut, had been struck by rockets. 

Several barrages have fallen in the northern Bekaa Valley and on Sunday two rockets were fired at the Hezbollah stronghold of southern Beirut after Hezbollah leader Hassan Nasrallah vowed his fighters would battle in Syria to victory whatever the cost. 

Israeli soldiers were scouring the northern part of the country Monday after reports that a rocket was fired toward the area from southern Lebanon.

Lebanese and Israeli media, citing security sources in both countries, reported that residents in the Marjayoun area of Lebanon, about six miles from the Israeli border, heard either the launch or the sound of a missile streaking through the air.

An IDF spokesman said residents of Metula, Israel, then heard an explosion, according to The Jerusalem Post.

"We haven't opened the bomb shelters, but we are ready," the newspaper quoted an IDF spokesperson as saying.

It was not clear who fired the rocket or mortar.

IDF teams found no sign of an exploded rocket or other projectile Sunday night and were searching again Monday, Reuters reported.

The incident comes as tensions from Syria have boiled over into Lebanon, where the militant group Hezbollah has vowed to support Syrian President Bashar Assad in the two-year civil war that has claimed more than 70,000 lives, according to U.N. estimates.

Israel, which keeps a wary eye on Hezbollah, has launched airstrikes in Syria that it says were aimed at the militant group and not the Syrian government.

Israel has repeatedly said that it would not allow long-time enemy Hezbollah to obtain sophisticated weapons.

There are also fears that Hezbollah’s backing of Assad could further inflame sectarian violence in Lebanon.

On Sunday, two missiles struck a Shiite Muslim area in southern Beirut that is considered a Hezbollah stronghold. Sunni Muslims in Lebanon tend to support the rebel forces fighting Assad.

NBC News' Lawahez Jabari and Reuters contributed to this report.

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Bilal Hussein / AP

Pro-Syrian-government fighters from Lebanon stand guard at the border of the two countries on April 12. The head of Lebanon-based Hezbollah has threatened that his heavily armed group, backed by Iran, may become further involved in the battle against forces trying to topple Syrian President Bashar Assad.

BEIRUT -- The leader of Lebanon's Hezbollah militant group said Tuesday that Syrian rebels will not be able to defeat President Bashar Assad's regime militarily, warning that Syria's "real friends," including his Iranian-backed militant group, were ready to intervene on the government's side.

Hezbollah, a powerful Shiite Muslim group, is known to back Syrian regime fighters in Shiite villages near the Lebanon border against the mostly Sunni rebels fighting to topple Assad. The comments by Sheik Hassan Nasrallah were the strongest indication yet that his group was ready to get far more involved to rescue Assad's embattled regime.

"You will not be able to take Damascus by force and you will not be able to topple the regime militarily. This is a long battle," Nasrallah said, addressing the Syrian opposition.

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A look back at the conflict that has overtaken the country.

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"Syria has real friends in the region and in the world who will not allow Syria to fall into the hands of America or Israel."

Hezbollah and Iran are close allies of Assad. Rebels have accused them of sending fighters to assist Syrian troops trying to crush the two-year-old anti-Assad uprising, which the U.N. says has killed more than 70,000 people.

Deeper and more overt Hezbollah involvement in the Syrian conflict is almost certain to threaten stability in Lebanon, which is sharply split along sectarian lines, and between supporters and opponents of Assad. It also risks drawing in Israel and Iran into a wider Middle East war.

Nasrallah said Tuesday there are no Iranian forces in Syria now, except for some experts who he said have been in Syria for decades. But he added: "What do you imagine would happen in the future if things deteriorate in a way that requires the intervention of the forces of resistance in this battle?"

Hezbollah has an arsenal that makes the group the most powerful military force in Lebanon, stronger than the national army. Its growing involvement in the Syrian civil war is already raising tensions inside the divided country and has drawn threats from enraged Syrian rebels and militants.

Nasrallah also said his fighters had a duty to protect the holy Shiite shrine of Sayida Zeinab, named for the granddaughter of Islam's Prophet Muhammad and located south of Damascus.

He said rebels have captured several villages around the shrine and have threatened to destroy it.

"If the shrine is destroyed things will get out of control," Nasrallah said, citing the 2006 bombing of the Shiite al-Askari shrine in the Iraqi city of Samarra. That attack was blamed on al Qaeda in Iraq and set off years of retaliatory bloodshed between Sunni and Shiite extremists that left thousands of Iraqis dead and pushed the country to the brink of civil war.

In recent weeks, government troops have overrun two rebel-held Damascus suburbs and a town outside the capital. They also have captured several villages near the border with Lebanon as part of their efforts to secure the strategic corridor running from Damascus to the Mediterranean coast, which is the heartland of the president's Alawite sect, an offshoot of Shiite Islam.

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TEL AVIV, Israel - A helicopter carrying Israeli Prime Minister Benjamin Netanyahu was reportedly forced to land in the north of the country after an unmanned drone was spotted trying to infiltrate Israel's airspace.

The prime minister's helicopter took off after the drone was shot down, according reports in Haaretz and Ynetnews. 

"The (unmanned aerial vehicle) was tracked by IDF ground and aerial surveillance for the duration of its flight path as it attempted to approach Israel's coast," the Israeli Defense Forces, or IDF, said in a statement.  "Israel Air Force aircraft intercepted the UAV and successfully downed the target five nautical miles off the coast of the northern Israeli city of Haifa."

The IDF declined to confirm Israeli media reports that Netanyahu's helicopter landed, but the prime minister did issue a statement shortly after news of the incident was released.

"I view with utmost gravity this attempt to violate our border. We will continue to do everything necessary to safeguard the security of Israel's citizens," the prime minister said in a statement. 

The incident was the second time in seven months that a drone had been intercepted in Israeli airspace, the IDF said. It did not say where the drone originated, but during the 2006 Israeli war with Lebanon, Israeli jets intercepted two drones launched by Hezbollah, the Lebanese Shiite militant organization. 

"UAVs pose a serious threat to the State of Israel's security. The IDF will not tolerate any attempt to violate Israel's sovereignty or harm its security," the IDF statement added. 

The IDF said it was searching the area over which the drone was shot down on Thursday evening.

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Happy birthday, Israel! Now have some tofu

Wael Hamzeh / EPA

Supporters of the Salafist Sheikh Ahmad al-Assir take part in a rally showing solidarity with the Syrian people in Beirut, Lebanon, on Feb. 8.

Syria warned it may strike at rebels hiding in neighboring Lebanon if the Lebanese army does not act, the state news agency SANA said on Friday, the second anniversary of the civil war.

Syria's Foreign Ministry told its Lebanese counterpart late on Thursday that a "large number" of militants had crossed Lebanon's northern border into the Syrian town of Tel Kalakh over the past two days, SANA said.

"Syria expects the Lebanese side to prevent these armed terrorist groups from using the borders as a crossing point, because they target Syrian people and are violating Syrian sovereignty," the diplomatic cable said.

It said Syria's "patience is not unlimited," even though "Syrian forces have so far exercised restraint from striking at armed gangs inside Lebanese territory."

Fighting near the border resulted in a large number of casualties, SANA said, before the gunmen retreated into Lebanon.

Lebanon has a policy of "dissociation" from the two-year civil war in Syria but officials say they feel their country is increasingly at risk of being dragged into a conflict that the United Nations says has killed 70,000 Syrians.

Threat to Lebanon's existence
U.N. refugee agency chief Antonio Guterres said on Friday that the Syrian conflict threatens Lebanon's existence.

"The international community should recognize that the Syrian crisis represents an existential threat to Lebanon and should show Lebanon ... much stronger support than has happened until now," he told reporters in Beirut.

Lebanon, a nation of 4 million, fought its own devastating civil war from 1975 to 1990 and has sectarian tensions among Christians and Sunni and Shiite Muslims that have been heightened by the fighting in Syria.

Tensions between Lebanese groups that support the Syrian opposition and those that support Syrian President Bashar Assad have been intensifying and have sometimes turned violent.

The International Committee of the Red Cross appealed to foreign powers Friday to press combatants in Syria to halt attacks on civilians and aid workers, saying all sides were violating the Geneva Conventions. 

"Many atrocities against civilians have been reported or witnessed over the past two years, and we have also seen indiscriminate attacks against civilians and the targeting of health-care personnel and aid workers," said Robert Mardini, head of ICRC operations for the Near and Middle East. 

Meanwhile, European Union governments rejected a Franco-British push on Friday to lift an EU arms embargo to allow weapons supplies to Syrian rebels, voicing fears this could spark an arms race and worsen regional instability.

France and Britain found little support for their proposal to ease the embargo at an EU summit in Brussels, EU diplomats said, although they asked the bloc's foreign ministers to look again at the issue next week.

"Nobody really is interested (in lifting the embargo)," an EU diplomat said. "There is no prospect of change any time soon."

EU governments want to support the rebels, but many expressed fears on Friday that allowing weapons to flow to them could lead to arms falling into the wrong hands -- especially Islamist militants in the rebel ranks -- and lead Assad's backers to step up arms deliveries to his government.

European Council President Herman van Rompuy said leaders had asked their foreign ministers to look at the issue "as a matter of priority" at a March 22-23 meeting in Dublin. 

Reuters

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Lebanese troops clashed with Syrian rebels on the border between the two countries in what a security source told Reuters may have the first such incident between Lebanon's army and the rebels.

The clash occurred Sunday when a Lebanese border patrol spotted the rebel fighters along the border and the rebels opened fire to prevent the patrol from approaching, the Lebanese military source told Reuters. He said there were no casualties.

Although tensions have been high along various points of the Lebanon-Syria border, Sunday's incident may have been the first involving armed fighters.

In late September, a security incident involving Syrian rebels at a Lebanese checkpoint was played down by local residents and officials but initial reports suggested that shots had been fired.

The violence in Syria also spilled over to Turkey on Monday, as Turkey scrambled fighter jets after Syrian government forces bombed rebel positions in the frontier town of Ras al-Ain and stray shells flew into Turkish territory, Turkish security sources told Reuters.

PhotoBlog: Turkey scrambles jets as Syrian government forces bomb border town

Shells landed in the Turkish town of Ceylanpinar, which abuts Ras al-Ain, triggering panic, the sources told Reuters. It was not immediately clear whether the shells were fired by forces loyal to President Bashar Assad or by the rebels.

Slideshow: Syria uprising

Osman Orsal / Reuters

A look back at the violence that has overtaken the country

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Syrians risk lives in battle to protect nation's ancient sites

The uprising against the Assad family’s four decades of rule began 20 months ago. Opposition activists say the fighting has resulted in the deaths of some 40,000 people, according to The Associated Press.

Syria: No chemical weapons plan
On Monday, Syria said that it would not use chemical weapons against its own people after the U.S. warned it would take action against any such escalation.

The statements came amid media reports, citing European and U.S. officials, that Syria's chemical weapons had been moved and could be prepared for use in response to dramatic gains by rebels fighting to topple Assad.

"Syria has stressed repeatedly that it will not use these types of weapons, if they were available, under any circumstances against its people," the foreign ministry said.

Car bombs kill 34 in Syria suburb

The opposition believe that Assad could turn to heavier weapons and some have suggested he might use chemical weapons. 

U.S. Secretary of State Hillary Clinton had earlier warned that Washington would take action if Syria used the weapons.

"I am not going to telegraph any specifics what we do in the event of credible evidence that the Assad regime has resorted to using chemical weapons against their own people, but suffice to say, we are certainly planning to take action if that eventuality were to occur," she said during a visit to Prague Monday.

'Worst day in those people's lives'
On Sunday, opposition activists said that dozens were killed and wounded when government forces pounded rebel-held suburbs around Damascus with fighter jets and rockets.

The British-based Syrian Observatory for Human Rights gave a preliminary death toll for Sunday's fighting of 140.

Slideshow: Behind Syrian rebel lines

Machine guns operated by motorcycle brakes? Get a glimpse at the rebels fighting against Assad's forces in Syria's mountainous Jabal al-Zawiya area.

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More Syria coverage from NBC News

Activists said rocket fire struck towns close to the Damascus airport road, where rebels and the army had been locked in three days of clashes. Some described constant shelling, similar to carpet bombing, in towns like Beit Saham.

"It was frightening because it was the first time we heard continuous shelling. Really powerful explosions, one after the other, were shaking the area. I could see fire coming up from the town," said Samir al-Shami, from the opposition's Syrian Youth Union, speaking by Skype.

"This was the worst day in those people's lives," he added.

Reuters and The Associated Press contributed to this report.

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