The United States is gearing up for what may be the last major American-run offensive of the Afghanistan war — a bid to secure the approaches to Kabul.

The U.S.-led spring offensive, expected to begin in the coming weeks, may be NATO's last chance to shore up Kabul's defenses before a significant withdrawal of combat troops limits its options.

---

The focus will be regions that control the main access routes, roads and highways into the ancient city from the desert south and the mountainous east. These routes are used not only by traders carrying goods from Pakistan and Iran but also by militants, including the Taliban.

The Taliban made their intentions clear over the weekend, mounting spectacular coordinated attacks that spawned an 18-hour battle with Afghan and NATO forces.

While bombings and shootings elsewhere in Afghanistan receive relatively little attention, attacks in the capital alarm the general population, undermine the government's reputation and frighten foreigners into fleeing the country.

Kabul fighting ends after 18 hours of intense gunfire

That's why insurgents on Sunday struck locations that were so fortified they could cause little or no damage, including the diplomatic quarter, the parliament and a NATO base.

"These are isolated attacks that are done for symbolic purposes, and they have not regained any territory," U.S. Defense Secretary Leon Panetta said Monday.

The strategy in eastern Afghanistan involves clearing militants from provinces such as Ghazni, just south of the capital. The pivotal region links Kabul with the Taliban homeland in the south and provinces bordering Pakistan to the east.

NATO, under U.S. command, will also conduct more operations in eastern provinces such as Paktika and Paktia that are considered major infiltration routes to the capital from insurgent safe havens in Pakistan.

Afghan President Karzai slams NATO over 18-hour Kabul gunbattle

Afghan and U.S. officials blamed the Pakistan-based Haqqani network, which is part of the Taliban and has close links with al-Qaida, for the weekend attacks that left 36 insurgents, eight policemen and three civilians dead in Kabul and three eastern provinces.

But Army Gen. Martin Dempsey, chairman of the U.S. Joint Chiefs of Staff, said officials have not concluded whether the attacks emanated out of Pakistan.

Declining numbers of international troops in the coming months are also forcing coalition forces to focus less on remote and thickly populated places such as eastern Nuristan. They hope to move responsibility for those areas to the Afghan security forces.

Coalition forces last summer made gains in traditional Taliban strongholds such as Kandahar and Helmand provinces in the south, areas they must now hold with fewer troops.

By September, as many as 10,000 U.S. Marines are scheduled to leave Helmand and hand over the lead for security to Afghan forces in the former Taliban stronghold.

"It's going to be a very busy summer," Gen. John Allen, the top U.S. and NATO commander, said recently. "The campaign will balance the drawdown of the surged forces with the consolidation of our holdings in the south, continued combat operations" and an effort to push Afghan security forces into the lead.

The Afghan army and police are now in charge of security for areas home to half the nation's population, with coalition forces in a support role. The coalition hopes to keep handing over control until Afghan forces are fully in charge by the end of 2013, with all combat troops scheduled to withdraw from the country by the end of 2014.

The U.S. may retain a small number of forces past that date to help train and mentor the Afghan army and help with counterterrorism efforts.

There is very little appetite in Western countries for keeping troops in Afghanistan, but U.S. Ambassador Ryan Crocker said Sunday's attack shows the danger of withdrawing international forces too quickly.

"There's a very dangerous enemy out there with capabilities and with safe havens in Pakistan. To get out before the Afghans have a full grip on security, which is a couple of years out, would be to invite the Taliban, Haqqani, and al-Qaida back in and set the stage for another 9/11," Crocker said.

More world news from msnbc.com and NBC News:

Sources: Briton killed after threat to expose Chinese leader's wife

Tunisia still wants sun lovers, new Islamist government says

Sources: Briton killed after threat to expose Chinese leader's wife

Elite Secret Service agents among those suspended

Follow us on Twitter: @msnbc_world

A leading Iraqi politician has accused the country's prime minister of acting like Saddam Hussein in trying to silence opposition, saying he risks provoking a new fightback against dictatorship.

Iyad Allawi -- a former prime minister who leads the Sunni-backed Iraqiya bloc -- also claimed the United States had pulled out its troops "without completing the job they should have finished."

---

Allawi said that the current premier, Nuri al-Maliki, had used fabricated confessions to demand the arrest of the country's Sunni Muslim vice president, Tareq al-Hashemi.

Al-Hashemi, who has taken refuge in Iraq's autonomous Kurdish region, denies allegations he ordered bombings and shootings against his opponents. The move against him, on the very day U.S. troops left the country, threatens to upset a balance among Shiite, Sunni and Kurdish factions.

Speaking to Reuters two days after the final departure of the U.S. forces that ended Saddam's Sunni-dominated rule, Allawi called for international efforts to prevent al-Maliki, who is a Shiite, from provoking renewed sectarian warfare of the kind that killed tens of thousands in the years after Saddam fell in 2003.

"This is terrifying, to bring fabricated confessions," Allawi said shortly before leaving the Jordanian capital Amman to return to Iraq. "It reminds me personally of what Saddam Hussein used to do where he would accuse his political opponents of being terrorists and conspirators."

• Arrest order for Sunni VP in Iraq raises tensions

"We fear the return of dictatorship by this authoritarian way of governing. It's the latest in a build-up of atrocities, arrests and intimidation that has been going on a wide scale," said Allawi, who comes from the Shiite Muslim majority but who has drawn support heavily from disaffected Sunnis.

As prime minister for 10 months under U.S. occupation in 2004 and 2005, Allawi was accused of revealing an authoritarian streak himself. He later led the Iraqiya bloc to first place in last year's parliamentary election but ended up joining a coalition headed by al-Maliki, who retained the premiership.

• For 'the Sheik,' US pullout is cause for alarm

He said he would now try to unseat the prime minister in the legislature: "We have to make a move to bring about stability to the country by trying to find a substitute to Maliki through parliament," said Allawi, who repeated allegations that Shiite Iran is seeking control in Iraq now that U.S. forces have left.

"Maliki has crossed all red lines and Iraq is now facing a very, very serious and very difficult situation," he said.

'Very heart of democracy'
"We are watching events unfolding which are aimed at the very heart of democracy and stability," he added. "The Americans have pulled out without completing the job they should have finished. We have warned them that we don't have a political process which is inclusive of all Iraqis and we don't have a full-blown state in Iraq."

"We want to resolve issues between Iraqis in a peaceful way and we want to bring stability. Iraqis should fill the vacuum, rather than anybody else," Allawi said, in a reference to his view Iran is intent on filling a vacuum left by U.S. troops.

Iraq sits on a sectarian, Sunni-Shiite faultline that is generating conflict throughout the region, notably between Iran and Sunni-ruled Arab states like Saudi Arabia. While the overthrow of Saddam in Iraq bolstered Shiites, the uprising against Iran's Syrian ally President Bashar al-Assad could lead to power in Damascus shifting toward Syria's Sunni majority.

"The rise of sectarianism is already there," Allawi said. "We are witnessing the beginning of it and the influences of what is happening in the region is only adding fuel to the fire. My fear is that the Iraqi people will lose faith in the political process and sectarianism will prevail.

"Unless the international community and the region get involved and unless sense prevails, Iraq is heading towards a very big conflict."

Also Tuesday, al-Hashemi told a televised news conference that he has not committed any "sin" against Iraq and also described the charges as "fabricated." He accused al-Maliki of being behind a plot to smear him and declared that efforts at national reconciliation had been blown apart.

"I'm shocked by all these things," al-Hashemi told reporters in the northern city of Irbil. "I swear to God that al-Hashemi didn't commit any sin or do anything wrong against any Iraqi either today or tomorrow and this is my pledge to God."

He said the arrest warrant was a campaign to "embarrass" him. He blamed al-Maliki, although he did not say specifically what he believed the Shiite premier had done.

"Al-Maliki is behind the whole issue. The country is in the hands of al-Maliki. All the efforts that have been exerted to reach national reconciliation and to unite Iraq are now gone. So yes, I blame al-Maliki," he said.

The Iraqi prime minister effectively runs the Interior Ministry, where the charges originated.

Reuters and The Associated Press contributed to this report.

Updated at 6:10 p.m. ET

President Barack Obama stopped short of calling the U.S. effort in Iraq a victory in an interview taped Thursday with ABC News' Barbara Walters.

"I would describe our troops as having succeeded in the mission of giving to the Iraqis their country in a way that gives them a chance for a successful future," Obama said.

Iraqi citizens offered a more pessimistic assessment. "The Americans are leaving behind them a destroyed country," said Mariam Khazim of Sadr City. "The Americans did not leave modern schools or big factories behind them. Instead, they left thousands of widows and orphans."

The Iraq Body Count website says more than 100,000 Iraqis have been killed since the U.S. invasion. The vast majority were civilians.

Updated at 10:58 a.m. ET

BAGHDAD --  U.S. forces formally ended their nine-year war in Iraq with a low-key flag ceremony in Baghdad on Thursday.

"After a lot of blood spilled by Iraqis and Americans, the mission of an Iraq that could govern and secure itself has become real," Defense Secretary Leon Panetta said at the ceremony at Baghdad's still heavily fortified airport.

• Vote: How would you describe the war in Iraq?

Almost 4,500 U.S. soldiers and tens of thousands of Iraqis lost their lives in the war that began with a "Shock and Awe" campaign of missiles pounding Baghdad and descended into sectarian strife and a surge in U.S. troop numbers.

---

U.S. soldiers lowered the flag of American forces in Iraq and slipped it into a camouflage-colored sleeve in a brief outdoor ceremony, symbolically ending the most unpopular U.S. military venture since the Vietnam War of the 1960s and 70s.

Iraqi Prime Minister Nouri al-Maliki and President Jalal Talabani were invited to the ceremony but did not attend.

In addition to the dead, the war left 32,000 Americans wounded and cost the U.S. more than $800 billion.

• PhotoBlog: Symbolism and souvenirs at ceremony

The remaining 4,000 American troops will leave by the end of the year.

Bombings are still common. Experts are also concerned about the Iraqi security force's ability to defend the nation against foreign threats.

However, Panetta said veterans of the conflict can be "secure in knowing that your sacrifice has helped the Iraqi people to cast tyranny aside."

• NYT: Junkyard's secret account of massacre

Some Iraqi citizens offered a more pessimistic assessment. "The Americans are leaving behind them a destroyed country," said Mariam Khazim of Sadr City. "The Americans did not leave modern schools or big factories behind them. Instead, they left thousands of widows and orphans."

Gen. Lloyd Austin, the top U.S. commander in Iraq, and Army Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, also spoke during the ceremony.

• PhotoBlog: Troops head for home

Updated at 5:46 a.m. ET: Austin says Iraqis now have "unprecedented opportunities."

Updated at 5:42 a.m ET: "Since 2003, we have helped the Iraqi security forces grow from zero to 650,000-strong," Austin says.

Updated at 5:40 a.m. ET: Austin recalls how he was present when American forces secured the airfield where the ceremony is being held. "After 21 days of tough fighting, we ended Saddam Hussein's reign of terror," he adds.

Updated at 5:37 a.m. ET: Army Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, points out that the next time he visits Baghdad it will have to be at the invitation of the Iraqi government. "I kinda like that," he adds.

Updated at 5:32 a.m. ET: "This is not the end, this is the beginning," Panetta says. "May God bless Iraq, its people and its future."

Updated at 5:29 a.m. ET: "Let me be clear, Iraq will be tested in the days ahead -- by terrorism, by those who would seek to divide," Panetta says. "Challenges remain but the United States will be there to stand with the Iraqi people. We are not about to turn our backs on all that has been sacrificed and accomplished."

Updated at 5:26 a.m. ET: "Your sacrifice has helped the Iraqi people begin a new chapter in history, free from tyranny," Panetta says. "This outcome was never certain, particularly during the war's darkest days."

Updated at 5:23 a.m. ET: Panetta highlights the "heartbreak" of military families who watched their loved ones go off to war.

Updated at 5:18 a.m. ET: "It is a profound honor to be here in Baghdad," Panetta says at ceremony."No words, no ceremony can provide full tribute to the sacrifices that have brought this day to pass."

Updated at 5:16 a.m. ET: "We look forward to an Iraq that is sovereign, secure and self-reliant," US Ambassador to Iraq James Jeffrey says.

Published at 4:45 a.m. ET: After nearly nine years, 4,500 American dead, 32,000 wounded and more than $800 billion, U.S. officials prepared Thursday to formally shut down the war in Iraq — a conflict that U.S. Defense Secretary Leon Panetta said was worth the price in blood and money, as it set Iraq on a path to democracy.

Panetta stepped off his military plane in Baghdad Thursday as the leader of America's war in Iraq, but will leave as one of many top U.S. and global officials who hope to work with the struggling nation as it tries to find its new place in the Middle East and the broader world.

He and several other U.S. diplomatic, military and defense leaders will participate in a highly symbolic ceremony during which the flag of U.S. Forces-Iraq will officially be retired, or "cased," according to Army tradition.

During several stops in Afghanistan this week, Panetta made it clear that the U.S. can be proud of its accomplishments in Iraq, and that the cost of the bitterly divisive war was worth it.

"We spilled a lot of blood there," Panetta said. "But all of that has not been in vain. It's been to achieve a mission making that country sovereign and independent and able to govern and secure itself."

That, he said, is "a tribute to everybody — everybody who fought in that war, everybody who spilled blood in that war, everybody who was dedicated to making sure we could achieve that mission."

Panetta has echoed President Barack Obama's promise that the U.S. plans to keep a robust diplomatic presence in Iraq, foster a deep and lasting relationship with the nation and maintain a strong military force in the region.

As of Thursday, there were two U.S. bases and about 4,000 U.S. troops in Iraq — a dramatic drop from the roughly 500 military installations and as many as 170,000 troops during the surge ordered by President George W. Bush in 2007, when violence and raging sectarianism gripped the country. All U.S. troops are slated to be out of Iraq by the end of the year, but officials are likely to meet that goal a bit before then.

Read more about the Iraq withdrawal

• Post-US Iraq: Welcome to Shia-stan
• Iraqis unable to defend borders as US exits
• Iraqi voices: Patchwork electrical grid a symbol of country's disconnects
• Iraqi voices: Colonel helped with surge, then his past came calling
• A special homecoming from Iraq

The total U.S. departure is a bit earlier than initially planned, and military leaders worry that it is premature for the still maturing Iraqi security forces, who face continuing struggles to develop the logistics, air operations, surveillance and intelligence sharing capabilities they will need in what has long been a difficult neighborhood.

U.S. officials were unable to reach an agreement with the Iraqis on legal issues and troop immunity that would have allowed a small training and counterterrorism force to remain. U.S. defense officials said they expect there will be no movement on that issue until sometime next year.

Still, despite Obama's earlier contention that all American troops would be home for Christmas, at least 4,000 forces will remain in Kuwait for some months. The troops will be able to help finalize the move out of Iraq, but could also be used as a quick reaction force if needed.

Bombings and attacks have eased since American and Iraqi security forces weakened insurgents. But roadside bombs, car bombs and assassinations still kill and maim almost every day.

A frail economy, constant power shortages, scarce jobs and discontent with political leaders all fuel uncertainty among Iraqis.

"Thanks to the Americans. They took us away from Saddam Hussein, I have to say that. But I think now we are going to be in trouble," said Malik Abed, 44, a vendor at a Baghdad fish market. "Maybe the terrorists will start attacking us again."

Read more content from msnbc.com and NBC News:

• Post-US Iraq: Welcome to Shia-stan
• Nazi hunters boost drive to find aging war criminals before they die
• Pakistan opposition leader: War on terror creating extremists
• Wild monkeys to detect radiation at Fukushima
• North Korea's heir apparent's hair apparent as fashion hit
• UN chief defends NATO, calls for action on Syria
• Rebellious Chinese village under siege by police
• Iraqis unable to defend their borders as US exits

The Associated Press, Reuters, NBC News and msnbc.com staff contributed to this report.

Story updated 12pm ET/9am PT: President Obama welcomed Iraqi Prime Minister Nuri al-Maliki to the White House Monday. Sitting side by side in the Oval Office, the two leaders posed briefly for cameras but did not make statements. They will hold a news conference together later.

Story published 6.30am ET/3.30am PT:

WASHINGTON - With the U.S. troop withdrawal from Iraq in its final days, President Barack Obama and Iraqi Prime Minister Nouri al-Maliki will meet at the White House Monday to discuss the next phase of the relationship between their countries.

They will have plenty to discuss.

---

The withdrawal of all American troops on Dec. 31 marks the end of a nearly nine-year war that has been deeply divisive in both the U.S. and Iraq. While Obama and al-Maliki have pledged to maintain strong ties, the contours of the partnership between Washington and Baghdad remain murky, especially with Iran eager to assert influence over neighboring Iraq. And serious questions remain about Iraq's capacity to stabilize both its politics and security.

Yet the end of the war still marks a promise kept for Obama, one the White House is eager to promote. In addition to his meeting with al-Maliki, Obama will mark the milestone Wednesday when he speaks to troops at North Carolina's Fort Bragg. And he thanked service members and their families for their sacrifices when he attended the annual Army-Navy football game Saturday.

As of late last week, the number of U.S. troops in Iraq had dwindled to about 8,000, down from 170,000 at the war's peak in 2007.

• Story: NYT: Detainee in Iraq poses dilemma as US exit nears

Monday's meeting between Obama and al-Maliki is expected to focus heavily on how the U.S. and Iraq will continue to cooperate on security issues without the presence of American troops. Iraqi leaders have said they want U.S. military training help for their security forces but have been unable to agree on what type of help they'd like or what protections they would be willing to give American trainers.

The White House said Obama and al-Maliki would also discuss cooperation on energy, trade and education.

Obama and al-Maliki will also hold a joint news conference at the White House, then lay wreaths at Arlington National Cemetery, where some of the nearly 4,500 Americans killed in the Iraq war are buried.

 

Iranian influence could grow
Looming over the talks are concerns among U.S. officials over how Iraq's relationship with Iran will develop with a significantly smaller U.S. presence in the region.

Al-Maliki has insisted that Iraq will chart its future according to its own national interests, not the dictates of Iran or any other country. But some U.S. officials have suggested that Iranian influence in Iraq would inevitably grow once American troops depart. Both countries have Shiite majorities and are dominated by Shiite political groups. Many Iraqi politicians spent time in exile in Iran during Saddam's repressive regime, and one of al-Maliki's main allies — anti-American cleric Muqtada al-Sadr — is believed to spend most of his time in Iran.

Jon Alterman, director of the Middle East Program at the Center for Strategic and International Studies, said how Baghdad chooses to orient itself will significantly influence the future of Iraq's relationship with the U.S.

• Story: US on Iraq security: 'We really don't know what's going to happen'

"A lot of this really comes down to, what kind of role is Iraq going to play in regional security?" Alterman said. "Is it going to be a place where bad people come and go, or is it going to play a role in calming down a region that needs some calming down?"

The first hints as to how Iraq will assert itself in the region may come from how it handles the troubles in Syria, where a bloody government crackdown on protesters has killed more than 4,000 people, according to the United Nations.

The Obama administration has called for Syrian President Bashar Assad to step down. But Iraq has been much more circumspect, with al-Maliki warning of civil war if Assad falls and abstaining from Arab League votes suspending Syria's membership and imposing sanctions. Those positions align Iraq more closely with Iran, a key Syrian ally.

The U.S. has warned Iraq's neighbors that even though American troops are leaving, the U.S. will maintain a significant presence there. About 16,000 people are working at the U.S. embassy in Baghdad, making it America's largest mission in the world.

Associated Press writer Rebecca Santana in Baghdad contributed to this report.

More content from msnbc.com and NBC News:

• NBC: Pakistan says US drones in its air space will be shot down
• Romney and Gingrich spar early at GOP debate
• 2011's weather disasters rack up $12 billion bill
• Giant Eurobank accused of gouging US consumers
• Friend: Va. Tech shooter had visited gun range
• Cops raid Occupy San Francisco at Federal Reserve