updated 7/17/2009 7:22:50 PM ET 2009-07-17T23:22:50

Iran is blocking U.N. nuclear agency attempts to upgrade monitoring of its atomic program while advancing those activities to the stage that the country would have the means to test a weapon within six months, diplomats told The Associated Press Friday.

The diplomats emphasized that there were no indications of plans for such a nuclear test, saying it was highly unlikely Iran would risk heightened confrontation with the West — and chances of Israeli attack — by embarking on such a course.

But they said that even as Iran expands uranium enrichment, which can create fissile nuclear material, it is resisting International Atomic Energy Agency attempts to increase surveillance of its enrichment site meant to keep pace with the plant's increased size and complexity.

For Iran to amass enough fissile material to conduct an underground test similar to North Korea's 2006 nuclear explosion, it would likely have to kick out monitors of the IAEA — the U.N. nuclear agency — from its one known uranium enrichment site at Natanz. Technicians then could reconfigure the centrifuges now churning out nuclear-fuel grade enriched uranium to highly enriched, weapons-grade material.

Iran is unlikely, however, to want to do that. Such a move would immediately set off international alarm bells and could bridge rifts on how strongly to react — Russia and China, which have resisted Western calls to increase pressure on Iran over its nuclear defiance, would likely endorse more sweeping U.N sanctions and other penalties.

Secret site?
With the U.N. nuclear agency strictly limited in its nuclear monitoring of Iran, the existence of a hidden enrichment site that could supply the weapons-grade uranium needed for a nuclear weapons test is also possible.

IAEA chief Mohamed Elbaradei has repeatedly warned that his agency cannot guarantee that Iran is not hiding nuclear activities. Iranian nuclear expert David Albright on Friday put the chances that such a secret site exists at "50-50."

But even a hidden enrichment plant meant to upgrade material to weapons level would likely have to be fed with low-enriched uranium from the Natanz site. So transporting that material would not escape the agency's detection.

In any case, international action — and possible Israeli attack — would be triggered at the latest by a nuclear test explosion.

Iran is still considered years away from developing a reliable nuclear warhead delivery system. So tipping its hand with a nuclear test, should it want to own such weapons, would make little sense.

"We are talking here not of intent but capability," said one of two western diplomats accredited to the International Atomic Energy Agency. Like his colleague from another country, this diplomat — who has access to intelligence on Iran's nuclear program — demanded anonymity in exchange for discussions of the highly confidential issue.

Weapons-grade material
Since its clandestine enrichment efforts were revealed more than six years ago, Iran has steadily increased activities at its cavernous underground facility at Natanz, a city about 300 miles south of Tehran.

An IAEA report circulated last month said nearly 5,000 centrifuges were now enriching at Natanz — about 1,000 more than at the time of the last agency report, issued in February — with more than 2,000 others ready to start enriching.

Iran says it is interested in producing only low-enriched uranium for fuel use, not highly enriched material for the fissile core of nuclear weapons, and the U.N. nuclear agency has detected no effort at Natanz to contravene that assertion.

Still, if Iran decided to risk an international crisis, it has the means to make weapons-grade uranium.

Most experts estimate that the more than 1,000 kilograms — 2,200 pounds — of low-enriched uranium Iran had accumulated by February was enough to produce enough weapons-grade material through further enrichment for one nuclear weapon.

And as Iran expands its operations at Natanz, its potential capacity to produce highly enriched uranium is also growing.

Centrifuges in operation
Albright's Washington-based Institute for Science and International Security last month estimated that with the nearly 5,000 centrifuges then operating Iran could accumulate enough material to produce weapons-grade uranium for two warheads by February 2010 — or sooner, if it brought the more than 2,000 additional machines on line immediately.

But one of the diplomats said Iran had already brought more centrifuges into full operation. And the other said that in any case, a test explosion could occur even sooner.

The six-month time frame confirmed to the AP Friday was first mentioned last week by the German magazine Stern, which cited Germany's Bundesnachrichtendienst, its main intelligence branch.

Albright said Friday six months are "in line with our estimates."

Iran steadfastly refuses to stop enriching despite the imposition of three rounds of economic, trade and financial sanctions by the U.N. Security Council. And worries have been heightened by the country's refusal to grant the U.N. nuclear agency broadened monitoring rights of its steadily increasing Natanz operations.

An International Atomic Energy Agency report last month touched on those concerns.

It said the agency had informed Iran that, due to the growth in enrichment capacity and output, it was seeking "improvements to the containment and surveillance measures" it now had at hand. And a senior U.N. official said expansion at Natanz "makes it increasingly difficult to do the surveillance" needed to ensure none of the material produced is being diverted.

No more cameras
To do its work at Natanz, the agency relies in part on monitoring by cameras and on inspections meant to give the Iranians a minimum of time between the announcement of the visit and the arrival of the inspectors — methods the agency would like to expand.

Diplomats last month told the AP that Iran's refusal to allow any additional cameras was a setback, along with its recent delay of an unannounced International Atomic Energy Agency inspection.

Since then, Iran has refused to grant broader monitoring rights, said one of the diplomats Friday.

He said it has also refused agency requests to separate operations at Natanz, where enrichment occurs in the same space as centrifuge repairs and setups of new chains of linked centrifuges, creating chaotic scenes that are difficult to monitor.

"It is really difficult for them to figure out what's happening, given the mix of different things going on," said the diplomat. He said that as of a week ago "Iran was not cooperating."

Image: Ali Akbar Salehi
Joe Klamar  /  AFP - Getty Images file
Ali Akbar Salehi has been appointed the head of the Atomic Energy Organization of Iran.

New chief
Meanwhile, Iranian President Mahmoud Ahmadinejad has appointed a new chief for the country's nuclear program, following the abrupt resignation of its veteran head, the official IRNA news agency reported Friday.

Ali Akbar Salehi, a U.S.-educated physicist who was Iran's former envoy to the U.N. nuclear watchdog agency, is replacing Gholam Reza Aghazadeh as the new vice president and the head of the Atomic Energy Organization of Iran, IRNA said.

Officials gave no reason for Aghazadeh's resignation , but he has long been close to reformist opposition leader Mir Hossein Mousavi, who claims to be the victor in June 12 presidential elections and has called Ahmadinejad's government illegitimate.

The replacement is unlikely to bring any change in the nuclear policy or impact the standoff between Iran and the West over the country's nuclear program since head of the nuclear program is not directly involved in negotiations, and ultimately all decisions on policy lie with Supreme Leader Ayatollah Ali Khamenei.

From his years as envoy to the U.N.'s International Atomic Energy Agency, Salehi is well-known to Western diplomats and to U.N. officials. His most high profile moment came in 2003 when 18 years of Iran's clandestine nuclear activities were exposed, putting Iran's nuclear issue at the top of the IAEA Board of Governors agenda.

Salehi holds a doctorate in nuclear physics from the Massachusetts Institute of Technology in the United States. He was also associate professor and chancellor of Sharif University of Technology in Tehran.

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