Even as a leaked report on Iran's nuclear program cites a string of safeguard "failures," Iran is enhancing its cooperation with UN inspectors of the International Atomic Energy Agency (IAEA) and trying to mollify deepening concerns in Russia and the US that it harbors secret nuclear-weapons ambitions.
An IAEA team arrived in Iran Saturday to take samples to test Iran's stated policy of transparency. Revelations in the past year about swift Iranian progress in uranium enrichment and previously unknown advanced facilities are raising new questions among nuclear experts.
Russia is Iran's top nuclear business partner and the builder of a controversial $1 billion reactor at Bushehr. But after years of defending Iran's nuclear program as peaceful, Russia appears to be undergoing an change in official thinking.
British Prime Minister Tony Blair set off a firestorm when he announced last week that Moscow had imposed new conditions on Iran. Russia would not send nuclear fuel to Iran unless the Islamic republic signed the nuclear Non-Proliferation Treaty (NPT) additional protocol, a measure that would enable stringent IAEA inspections of undeclared sites.
Senior Russian and Iranian officials have since denied that any new condition exists.
They said instead that the two nations have only to hammer out details of an accord that requires Iran to return all spent fuel to Russia.
But Russia has been embarrassed and surprised by the scale of an undeclared gas centrifuge-enrichment plant at Natanz, 200 miles south of Tehran.
A uranium-conversion facility is also coming on line at Isfahan, and Iran declared to the IAEA last month that it plans to build a heavy-water research reactor.
And in February, President Mohamed Khatami announced that Iran was developing its own uranium deposits at mines near Yazd, in the central part of the country.
"Russian officials have made a huge evolution in understanding the threat from Iran" and are making "progress toward the US position," says Anton Khlopkov, an Iran expert at the PIR Center in Moscow, a military-research institute that predicts a "worst-case scenario" of Iran building a nuclear weapon by 2006, in a report soon to be released.
"Not only US but Russian experts were really surprised by the information about these two sites and these two plants," Mr. Khlopkov says of the enrichment facilities. "Russia and the US should engage with European experts to find the source of such technologies ... maybe in North Korea or Pakistan."
The US has labeled Iran part of an "axis of evil," and is pushing for the 35-member board of the IAEA to declare Iran in violation of the NPT when it meets in Vienna on June 16.
Addressing the issue Sunday during a special session of Iran's parliament, Foreign Minister Kamal Kharrazi declared that it was strictly forbidden for Muslims to use any weapon of mass destruction.
"We have no nuclear weapons program and we have said this frankly and clearly so many times," Mr. Kharrazi said. "We have a security doctrine that is without nuclear weapons."
But a tough IAEA report drawn up for the Vienna meeting was widely leaked on Friday. It found that "Iran has failed to meet its obligations ... with respect to the reporting of nuclear material [imported from China in 1991]." The IAEA also noted that the failures were being "rectified" by Iran.
Though Iran dismissed the findings as out of date, headlines and speculation about Iran's nuclear intentions are cutting deeply, even with allies.
For years, Russia stated that Iran was incapable of gas centrifuge enrichment. But during a February visit to the Natanz site - which Iran was not required to declare, according to the NPT, until 180 days before it planned to enrich uranium there - IAEA chief Mohamed ElBaradei found what he called a "sophisticated" program.
An article in the current issue of the Bulletin of the Atomic Scientists by two American experts notes that Iran has joined an "exclusive club" of some 10 nations that can build such centrifuges.
Some 160 centrifuges were already operational, with parts in place for 1,000 more. Portions of the facility are being built deep underground. The complete project would include some 5,000 - enough, experts say, to create weapons-grade material for several nuclear weapons per year.
Iran has also declared that it has worked with uranium metal - a substance rarely used for peaceful purposes but critical for weapons components - raising red flags for experts.
The leaked IAEA report makes clear that unless Iran signs the additional protocol, its ability to "provide credible assurances" about "undeclared nuclear activities is limited."
"Iraq clearly got caught, so it revealed quite a few things," says David Albright, a nuclear expert and former IAEA inspector in Iraq, who is head of the Institute for Science and International Security in Washington and an author of the Bulletin article.
"In total," he adds, "it looks like it was putting together a nuclear weapons program."
Still, Iran is not in breach of the NPT, Mr. Albright says, and most on the IAEA board "will want to give Iran more time, to see if they really are turning a corner, or just revealing what they have to."
US State Department spokesman Richard Boucher on Friday said the IAEA report was "deeply troubling."
While Iranian officials have long denied nuclear-weapon ambitions, many declare their right to a create such weapons, noting that they live in tough neighborhood in which Israel, Pakistan, and India all have the bomb.
Kharrazi on Sunday linked Iran's nuclear progress to national pride, calling it "the source of our power and every Iranian is proud of that."
Already, many Iranians embrace the idea of being a nuclear-armed regional power.
"The people of Iran actually believe that if we have a nuclear weapon, it is a good idea, because it is a deterrent ... and we would be treated much more politely by the rest of the world," says an Iranian observer contacted in Tehran, who asked not to be named. "Why shouldn't we have that?"