Iran's Presidency Office / Hando / EPA file

A picture released by the Iranian government shows Iran President Mahmoud Ahmadinejad inspecting the Natanz nuclear plant in central Iran in 2007.

In a move seen as a defiant step as world powers look to rein in Iran's nuclear program, the county has started installing sophisticated centrifuges at its main uranium enrichment plant, a U.N. nuclear report confirmed on Thursday.

The International Atomic Energy Agency (IAEA) said that 180 of the so-called IR-2m centrifuges and empty centrifuge casings had been hooked up at the plant near the town of Natanz, Reuters reported Thursday. The centrifuges were not yet operating.

The advanced centrifuges are expected to accelerate Iran's ability to process more highly enriched uranium. The West and Israel are fearful that such material could be used to build an atomic weapon.

"This is yet another provocative step by Iran and will only invite further isolation by the international community," said Tommy Vietor, spokesman for the National Security Council. "We continue to believe there is time and space for diplomacy to work, but actions like this undercut the efforts of the international community to resolve its concerns over Iran's nuclear program."

For its part, Iran claims it is only increasing its stockpiles of refined uranium for peaceful purposes — in order to produce energy.

Still, the White House and intelligence officials had been anticipating the report and Iran itself had in fact notified the U.N. nuclear watchdog in January that it intended to take the step.

According to Reuters, the confidential report also said Iran had increased to 367 pounds the amount of uranium refined to a purity of 20 percent. That is a level Tehran says it needs for conversion to reactor fuel. In August 2012, the U.N. watchdog group had reported that Iran had stockpiled 200 pounds of the 20-percent material.

About 530-550 pounds of uranium enriched to a level of 20 percent is required for a single nuclear weapon. That would need to be further refined to about 55 pounds of uranium enriched to a 90 percent purity level, according to the U.N. watchdog.

But the IAEA report also said Iran in December resumed converting some of its more highly enriched uranium to powder that would be used in the production of reactor fuel, Reuters reported. That was seen as an positive step in light of Western concerns.

Israel has warned that it might bomb Iran's nuclear sites as a last resort. In a speech to the U.N. in September, Israeli Prime Minister Benjamin Netanyahu said that with a nuclear armed Iran, no one in the world would be safe.

This week, Israel's UN Ambassador Michael Oren told MSNBC's "Morning Joe" that this summer is the "red line" beyond which Israel would not be confident Iran wasn't secretly reaching the point of no return in its nuclear progress. 

But a resumption of conversion to fuel, experts told Reuters, means the Israeli "red line" for action could be postponed. 

Next week, The Unites States, Russia and European allies are set to resume negotiations with Iran on its nuclear program. The negotiations will take place in Kazakhstan.

NBC News' Andrea Mitchell and Reuters contributed to this report.

Discriminatory implementation of the nuclear Non-Proliferation Treaty (NPT) has left many countries feeling that being a party to the anti-atom bomb pact hinders cooperation in the field atomic energy, Iran's U.N. ambassador said on Monday.

Western diplomats and analysts have long expressed concern that Iran might one day follow North Korea's example and pull out of the NPT and produce a bomb. North Korea withdrew from the treaty in 2003 and tested nuclear devices in 2006 and 2009.

Speaking at a meeting of the U.N. General Assembly on the annual report of the International Atomic Energy Agency (IAEA), Iranian Ambassador Mohammad Khazaee sought to assure countries that despite Tehran's reservations about the way the treaty is enforced, Iran does not plan to pull out.

"Iran ... is fully committed to its legal obligations, and its nuclear activities are, and have always been, exclusively for peaceful purposes," Khazaee said. He added that Tehran considers development of the full nuclear fuel cycle an "inalienable right" under the NPT.

Western intelligence sees 'small signs of wavering' on Iran nuclear policy

Western powers and their allies fear Iran is amassing the capability to produce atomic weapons, an allegation Tehran rejects. The Security Council has imposed four rounds of sanctions on Iran for refusing to halt nuclear-fuel work, but Tehran has pressed ahead with uranium enrichment.

Khazaee accused the United States, Britain and France of supplying Israel - which is not a party to the 1970 treaty aimed at preventing the spread of nuclear arms and is widely assumed to be the Middle East's sole nuclear power -- with atomic "assistance and cooperation."

"The application of a discriminatory, selective, highly restrictive and politically motivated approach in nuclear cooperation ... has given rise to this impression that being an NPT party is not a privilege, because rather than facilitating, it impedes nuclear cooperation," he said.

Israel neither confirms nor denies having nuclear arms.

Nuclear discrimination?
In a written message to the 193-nation assembly, IAEA Director-General Yukiya Amano reiterated his oft-stated concerns about the agency's decade-long probe of Iran's nuclear program.

"Iran is not providing the necessary cooperation to enable us to provide credible assurance about the absence of undeclared nuclear material and activities," his statement said. "Therefore, we cannot conclude that all nuclear material in Iran is in peaceful activities."

Slideshow: Everyday life in Iran

At schools, in shops, and on the streets of big cities and small towns, daily life plays out in Iran.

Launch slideshow

Some analysts agree the non-proliferation regime is discriminatory, since the five permanent U.N. Security Council members -- Britain, China, France, Russia and the United States -- are all permitted to maintain nuclear arsenals, although they have pledged under the NPT to negotiate on eradicating such arms.

Complete World coverage on NBCNews.com

Russia and the United States, which possess the bulk of the world's nuclear weapons, have reduced the size of their atomic arsenals, although both still possess thousands of warheads. None of the other five permanent members has yet given up their capability.

The NPT bars non-nuclear weapons states from developing or acquiring them.

The IAEA statement expressed similar frustrations about the agency's investigations into North Korea and Syria. It said Pyongyang's statements about uranium enrichment and construction of a light-water reactor were "deeply troubling."

In a typically fiery speech, North Korea's deputy U.N. envoy Ri Tong Il told the assembly the IAEA was irrelevant to the situation in Asia because the agency was a puppet of Washington.

"The situation on the Korean peninsula is on the brink of explosion and nobody knows when the war will break out," he said, adding that the United States and South Korea were to blame. He said six-party aid-for-disarmament talks with the United States, China, Russia, Japan and South Korea were nearly "dead."

With Iran issue simmering, Israeli Prime Minister Netanyahu calls early elections

North Korea expelled IAEA inspectors at the end of 2002 when it restarted its mothballed Yongbyon nuclear facilities.

Pakistan, which like its neighbor India has nuclear arms but is not a member of the NPT, also complained to the General Assembly about the discriminatory way in which atomic technology is made available to some states, but not others.

"Pakistan believes in an equitable, non-discriminatory and criteria-based approach to advance the universally shared goals of non-proliferation and promotion of peaceful uses of nuclear energy," Pakistani Ambassador Masood Khan said.

Pakistan, which was embarrassed after it was revealed in 2003 that Pakistani technology had been sold to both Iran and North Korea, has long been irritated by a bilateral U.S.-India deal on the transfer of civilian nuclear technology to India.

That agreement went against a long tradition according to which countries producing nuclear technology pledged not to supply atomic equipment to states outside the NPT, or to treaty signatories in violation of it.

Frustrated by its status as a nuclear pariah, Pakistan has been turning to China for nuclear cooperation.

The IAEA statement also said that the agency continued to have questions about a site in Syria's desert Deir al-Zor region that U.S. intelligence reports say was a nascent, North Korean-designed reactor designed to produce plutonium for nuclear weapons before Israel bombed it in 2007.

Amano's statement reiterated his request for information about Deir al-Zor, which Syria says was a conventional military site, and other locations in Syria.

More world stories from NBC News:

• Analysis: From Afghanistan to Venezuela, 2012 battle captivates
• Analysis: Despite bloodshed,White House candidates ignore Mexico
• Analysis: US loses patience with Syria opposition group
• Analysis: Suspicion of US rife as Romney, Obama batter China
• Meet Afghan female rapper, colonel who defy the odds
• Analysis: Israel, Iran name checks illustrate America's twin obsessions
• Chinese say one child is enough as Beijing weighs end of policy
• Analysis: Should next US president treat Russia as friend or foe?
• Expert: Tourists threaten Sistine Chapel's famous paintings

Follow World News from NBCNews.com on Twitter and Facebook

Iran has doubled the number of uranium enrichment machines it has in an underground bunker, a U.N. report said Thursday, showing Tehran has continued to defy Western pressure to stop its atomic work and the threat of Israeli attack.

The U.N. International Atomic Energy Agency (IAEA) said in its quarterly report on Iran that the number of centrifuges at its Fordow site -- buried deep underground to withstand any such hit -- had more than doubled to 2,140 from 1,064 in May. The new machines were not yet operating, it said.

“… as Iran is not providing the necessary cooperation… the Agency is unable to provide credible assurance about the absence of undeclared nuclear material and activities in Iran, and therefore to conclude that all nuclear material in Iran is in peaceful activities,” the report said.

“… the Agency considers it essential for Iran to engage with the Agency without further delay on the substance of the Agency’s concerns,” it added. “In the absence of such engagement, the Agency will not be able to resolve concerns about issues regarding the Iranian nuclear program, including those which need to be clarified to exclude the existence of possible military dimensions to Iran’s nuclear program.”

Iran's supreme leader repeated this week that Iran's nuclear program was entirely peaceful.

"Our motto is nuclear energy for all and nuclear weapons for none," Ayatollah Ali Khamenei told a developing nations summit in Tehran.

S. African telecom firm helped Iran evade US sanctions, documents show

But the expansion in enrichment infrastructure and the increasing in stockpiles of potent nuclear material revealed in the report will do nothing to allay fears or reduce the diplomatic sanctions and pressure on Iran.

The report showed that Iran had produced nearly 190 kg (418 pounds) of higher-grade enriched uranium since 2010, up from 145 kg (320 pounds) in May.

Slideshow: Everyday life in Iran

At schools, in shops, and on the streets of big cities and small towns, daily life plays out in Iran.

Launch slideshow

Iran says it needs this material, which is much purer than fuel needed for electricity generation, for a medical research reactor, but it also takes it significantly closer to making potential bomb material.

UN chief denounces Iran to its face over calls to destroy Israel

The IAEA also expressed concerns about Parchin, a military site south of the capital that it wants to inspect for evidence of past nuclear weapons development.

"Significant ground scraping and landscaping have been undertaken over an extensive area at and around the location," it said.

Five buildings had been demolished and power lines, fences and paved roads removed, the report said, "extensive activities" that would hamper its investigation if granted access.

"The activities observed... further strengthen the Agency's assessment that it is necessary to have access to the location at Parchin without further delay," the IAEA said.

Iran says Parchin is a conventional military facility and has dismissed the allegations about it as "ridiculous."

Foreign Minister Ali Akbar Salehi, meeting U.N. Secretary-General Ban Ki-moon in Tehran on Thursday, was quoted by Iranian state TV as saying: "The West has put sanctions on Iran for years, however the Iranian nation continues to resist and make progress."

A Western diplomat said the doubling of enrichment capacity at Fordow was a "worrying trend," showing that Tehran continued to expand its program.

Reuters contributed to this report.

More world stories from NBC News:

• Assad stays cool amid reports of bread-line slaughter
• Ex-Marine on her journey from homelessness to the Paralympics
• Red Cross halts most Pakistan aid in wake of beheading
• Unexploded WWII bomb disrupts Amsterdam airport
• Pakistani Christians live in fear after girl's blasphemy arrest
• 'A less polar pole': Arctic sea ice at record low
• Botched restoration turns Spanish church into tourist attraction

Follow World News from NBCNews.com on Twitter and Facebook

DigitalGlobe - ISIS

This satellite image from Friday shows earth displacement activity at the suspected high explosive testing site in Parchin, Iran. The U.N.'s nuclear watchdog has repeatedly asked Iran for access to the site as part of a long-stalled probe into suspicions that Tehran may be seeking the ability to assemble nuclear bombs.

VIENNA -- U.N. nuclear inspectors displayed new satellite imagery on Wednesday indicating that some small buildings had been dismantled and other possible clean-up work undertaken at an Iranian military site they want to visit.

One image from May 25 showed signs that "ground-scraping activities" had taken place at the Parchin facility, as well as the presence of a bulldozer, according to diplomats who attended a closed-door briefing by U.N. nuclear agency officials.

This will likely further strengthen Western suspicions that Iran is "sanitizing" the site of any incriminating evidence before allowing the International Atomic Energy Agency (IAEA) into the complex. "It is very clear," one Western envoy said.

Iran's IAEA envoy, Ali Asghar Soltanieh, dismissed such accusations by Western officials, telling reporters after the briefing that "this kind of noise and allegations are baseless".

Israel's Barak to NBC: Nuclear Iran unacceptable

The images released by the Institute for Science and International Security's (ISIS) could hurt a tentative deal between the U.N.'s atomic watchdog aimed at giving inspectors wide access to scientists, documents and facilities allegedly related to nuclear-weapons work, The Wall Street Journal reported. 

Wednesday's disclosure followed inconclusive talks between Iran and six world powers in Baghdad last week to address concerns about the nature of its nuclear activities, which Iran says are aimed at generating electricity.

The images were posted on ISIS's website hours after diplomats said the International Atomic Energy Agency showed what appeared to be similar imagery at a closed-door briefing in Vienna. 

The agency has been pressing Iran to allow inspectors to visit the Parchin military facility, which the IAEA thinks could have been involved in testing of high explosives, the Wall Street Journal reported.

Western envoys who attended Wednesday's briefing earlier told Reuters that two small side buildings at Parchin had been removed, and ISIS said its pictures from May 25 showed that they "have been completely razed."  

ISIS, which tracks Iran's nuclear program closely, said there were visible tracks in the images "made by heavy machinery used in the demolition process," adding that the two buildings had been intact in early April. 

The U.N. International Atomic Energy Agency (IAEA) has repeatedly asked Iran for access to Parchin as part of a long-stalled probe into suspicions that Tehran may be seeking the ability to assemble nuclear bombs, should it decide to do so. 

The Islamic state has so far refused to let inspectors visit the facility -- which it describes as a conventional military complex -- saying there must first be a broader framework agreement on how to address the IAEA's questions. 

Report: Iran using passenger jets to smuggle weapons to Syria, Lebanon

The Parchin complex is at the center of Western allegations that Iran has been conducting research and experiments that could serve a nuclear weapons development programme. The Islamic Republic has repeatedly denied any such ambition. 

Iran state TV: We'll build second nuclear plant

Last week, the IAEA said in a report issued to member states that satellite images showed "extensive activities" at the facility southeast of Tehran. 

Western diplomats said this was an allusion to suspected cleaning at Parchin. They have earlier cited other images showing recent activity at the site, including a stream of water, as suggesting Iran is trying to remove evidence. 

Iran, big powers agree to another round of nuclear talks

An IAEA report last November said Iran had built a large containment vessel in 2000 at Parchin in which to conduct tests that the U.N. agency said were "strong indicators of possible (nuclear) weapon development." 

It said a building was constructed around a large cylindrical object, a vessel designed to contain the detonation of up to 70 kg of high explosives. Diplomatic sources say the suspected tests likely took place about a decade ago. 

Last week, a senior Iranian official was quoted as saying the IAEA had not yet given good enough reasons to visit Parchin. 

Reuters contributed to this report.

More world news from msnbc.com and NBC News:

• Will crisis-hit Ireland rebel against harsh remedy for ailing Europe?
• 'Very clear' signs of Iran sanitizing military site, Western diplomat says
• Porn actor wanted for murder over body parts in Canada mail
• Tribesmen release two 2 US tourists kidnapped in Egypt
• Report: Hundreds detained in Tibet after self-immolations
• Israel's Barak tells NBC: 'A nuclear Iran is unacceptable'
• Was Flame virus written by cyberwarriors or gamers?
• Report: Iran using passenger jets to smuggle weapons to Syria, Lebanon
• Nelson Mandela makes rare appearance in home village
• Greek tragedy: Economic crisis sparks brain drain

Follow us on Twitter: @msnbc_world

Iran is to build a second nuclear power plant in the southern city of Bushehr, by early 2014, state television reported Sunday, according to news reports.

"Iran will build a 1,000-megawatt nuclear power plant in Bushehr next year," state television quoted Fereydoon Abbasi Davani, the head of Iran’s Atomic Energy Organisation, as saying, according to a report on Afghanistan news site Tolo News.

He was referring to the Iranian calendar year, running from March 2013 to March 2014, the site said.

The current Bushehr nuclear plant was started by German engineers in the 1970s, before Iran's Islamic Revolution, and was completed by Russia, which continues to help keep it running and provides fuel for it, Tolo News said.

Iran has repeatedly said in recent years that it is planning to build more nuclear power plants but nothing has been offered to show that any work is under way, according to a report by The Associated Press.

More world news from msnbc.com and NBC News:

• UN: 32 children, dozens of adults killed in Syrian town
• Budget cut overkill? Canada axes entire marine pollution program
• Weakened Fukushima nuclear pool is not unstable, Japan insists
• Scotland launches independence campaign with 007's support
• Runoff could take Egypt's voters on one of two very different paths
• Leftist tipped to be next Greek leader warns of 'Cold War' over austerity

Follow us on Twitter: @msnbc_world

VIENNA -- Six world powers called on Iran on Thursday to let international inspectors visit the Parchin military site where the U.N. nuclear watchdog says development work relevant to nuclear weapons may have taken place.

In a joint statement at a board meeting of the International Atomic Energy Agency (IAEA), the powers also voiced "regret" about Iran's stepped-up campaign to enrich uranium - activity which can have both civilian and military purposes.

"We urge Iran to fulfill its undertaking to grant access to Parchin," the statement said, referring to the military facility southeast of Tehran. Iran refused access to the complex during two rounds of talks with a senior IAEA team earlier this year.

Western diplomats suspect the Islamic state may now be trying to clean up the site to remove evidence of research with nuclear applications before possibly allowing inspectors in.

Iran asks to resume nuclear talks after year of impasse

The six powers handling the Iran nuclear issue are the United States, China, Russia, France, Germany and Britain.

An IAEA report last year revealed a trove of intelligence pointing to research activities in Iran of use in developing the means and technologies needed to assemble nuclear weapons, should it decide to do so.

One salient finding was information that Iran had built a large containment chamber at Parchin in which to conduct high-explosives tests that the IAEA said are "strong indicators of possible weapon development".

Slideshow: Everyday life in Iran

At schools, in shops, and on the streets of big cities and small towns, daily life plays out in Iran.

Launch slideshow

Stalling tactics
Iran, which says its nuclear program is purely for peaceful purposes, has dismissed intelligence reports suggesting it has a nuclear weapons agenda as forged and baseless.

It has suggested that the IAEA could get access to Parchin, but only after a broader deal is reached on how to address all outstanding issues between Tehran and the Vienna-based agency - an approach Western diplomats dismissed as a stalling tactic.

Iran says it will let UN nuclear sleuths visit key military site

The world powers' statement, agreed after intensive discussions within the often disunited group, also voiced backing for efforts to find a diplomatic solution to the long-running row.

Israel and the United States have threatened Iran with military strikes as a last-ditch way to stop it getting nuclear weapons.

The European Union's foreign policy chief, who represents the powers in dealings with Iran, said on Tuesday they had accepted Iran's offer to return to talks after a standstill of a year that seen increasingly bellicose rhetoric.

"We ... reaffirm our continuing support for a diplomatic solution to the Iranian nuclear issue and readiness to restart dialogue with Iran," the powers said in their statement, read out by China's envoy to the IAEA at the closed-door meeting.

"We call on Iran to enter, without preconditions, into a sustained process of serious dialogue which will produce concrete results." Iran has refused at previous talks to negotiate on the future of its nuclear activity.

On Thursday, an Israeli official said Israel has asked the United States for advanced "bunker-buster" bombs and refueling planes that could improve its ability to attack Iran's underground nuclear sites.

"Such a request was made" around the time of Israeli Prime Minister Benjamin Netanyahu's visit to Washington this week, the official said, confirming media reports.

But the official, who spoke on condition of anonymity given the sensitivity of the issue, played down as "unrealistic" reports that the United States would condition supplying the hardware on Israel promising not to attack Iran this year.

Netanyahu told Obama at a White House meeting on Monday that Israel had not yet decided on military action against Iran, sources close to the talks said.

More from msnbc.com and NBC News:

• 'I join the revolution': 1st senior Assad official defects
• 'Collar bomb' case: Investment banker pleads guilty
• One year after Fukushima, Japanese town is frozen in time
• Japanese tsunami survivor, 79, looks ahead
• Palestinian women allege abuses by Israeli security service

Follow us on Twitter: @msnbc_world

The Iranian government has blocked attempts to investigate its alleged atomic weapons work, the U.N.’s nuclear watchdog agency said Wednesday.

The U.N. International Atomic Energy Agency, or IAEA, expressed disappointment over a lack of progress during two days of talks in Tehran over Iran's disputed nuclear program and said its request to visit a military site had not been granted.

In the second such visit in less than a month, a senior team from the IAEA had traveled to Tehran to press Iranian officials to start addressing mounting concerns that the country may be seeking to develop atomic arms.

"During both the first and second round of discussions, the agency team requested access to the military site at Parchin. Iran did not grant permission for this visit to take place," the Vienna-based IAEA said in a statement after the talks Monday and Tuesday talks in the Iranian capital.

The statement was released early Wednesday, after the IAEA team left on a return flight to Vienna. The unusual timing — shortly after midnight in Europe — reflected the urgency the IAEA attached to the communique.

NYT: Mother visits American sentenced to death in Iran

Iran denies any interest in possessing nuclear weapons and says its atomic program is for peaceful purposes.

In the latest in a war of words between the West and Iran, an Iranian general warned Tuesday that the nation will pre-emptively strike anyone who threatens it.

The statement by Gen. Mohammed Hejazi continues the defiant tone Tehran has taken in its confrontation with Western countries that claim it is developing nuclear weapons.

"We do not wait for enemies to take action against us," said Hejazi, according to the semiofficial Fars news agency. "We will use all our means to protect our national interests."

Hejazi heads the military's logistical wing.

The U.S. and Israel have not ruled out strikes against Iranian nuclear facilities.

Iran also said Tuesday that a visiting U.N. team did not plan to inspect the country's nuclear facilities and would only hold talks with officials in Tehran.

The statement cast doubt on how well U.N. inspectors can gauge whether Iran is moving ahead with its suspected pursuit of nuclear weapons.

Iran threatens pre-emptive action amid nuclear tensions

The visit by the International Atomic Energy Agency team, which started Monday, is the second in less than a month.
Foreign Ministry spokesman Ramin Mehmanparast said the visiting IAEA team was made up of experts, not inspectors. He told reporters that the IAEA team was holding discussions Tuesday in Tehran to prepare for future cooperation between Iran and the U.N. watchdog. He said this cooperation is at its "best" level.

"The (title) of the members of the visiting delegation is not 'inspectors.' This is an expert delegation. The purpose of visit is not inspection," said Mehmanparast. "The aim is to negotiate about cooperation between Iran and the agency and to set a framework for a continuation of the talks."

Visits to Iranian nuclear sites were not part of the IAEA visit three weeks ago.

The latest IAEA trip came as Iran carried out air defense war games to practice protecting nuclear and other sensitive sites.

The official news agency IRNA said Monday that the four-day air defense war games — dubbed "Sarallah," or "God's Revenge" — were taking place in the south of the country and involved anti-aircraft batteries, radar and warplanes. The drill was to be held over 73,000 square miles near the port of Bushehr, the site of Iran's lone nuclear power plant.

Iran has held multiple air, land and sea maneuvers in recent months as the tensions increased.

The military maneuvers are viewed as a message to the West that Iran is prepared to defend itself against hostile measures and to retaliate — including warnings that it could cut the strategic Strait of Hormuz waterway off its southern coast with its naval forces.
Tehran is also under heavy economic pressure. Last month, the European Union imposed sanctions on Iran's fuel exports and froze its central bank assets. An oil embargo is set to begin in July.

Iranian officials said the country should respond by cutting off EU states early, before they can line up alternative buyers. Over the weekend, Tehran announced that it was pre-emptively cutting off exports to France and Britain.

 Reuters and The Associated Press contributed to this report.

More from msnbc.com and NBC News:

• Palestnians cheer pending release of hunger striker
• Venezuela's Hugo Chavez to undergo more surgery
• Wildlife officials fear 'epidemic' in rhino poaching
• Family photos lost in Japan tsunami are reunited with survivors