Iran has also admitted to importing parts for sophisticated P-2 centrifuges, which can enrich uranium to bomb-grade levels, going back on claims that it had made the parts domestically, according to a confidential report by International Atomic Energy Agency (IAEA) chief Mohamed ElBaradei, which was obtained by AFP.
And while Iran has insisted its P-2 is a research program, the IAEA said Iran had asked through a European intermediary about the possibility of buying 4,000 special magnets, or enough for 2,000 centrifuges.
Nuclear expert David Albright told AFP from Washington that Iran's "centrifuge story just doesn't hold up".
He said the numbers made it look like Iran rather than doing research was seeking "to go into serial production." Highly enriched uranium (HEU) can be nuclear fuel or the explosive in an atom bomb.
Particles of 36-percent HEU found at Farayand, a new site after IAEA inspectors had last year detected such particles at the Kalaye Electric Comany in Tehran, leave the IAEA unable to confirm Iran's claims the contamination was from imported equipment, probably from Pakistan, rather than a sign the Iranians may have been trying to enrich uranium on their own.
"This means they're probably lying about the origin of that 36 percent enriched uranium," a Western diplomat close to the IAEA said.
"Obviously they either imported the enriched uranium from abroad or it originated in their own enrichment," the diplomat said, mentioning that the HEU might be from a Russian research reactor.
The United States renewed accusations that Iran is secretly trying to develop nuclear weapons after the IAEA revelations.
State Department spokesman Richard Boucher said Washington's view was "borne out by the facts."
Iran must clear up these questions about uranium contamination and centrifuges if the international community is to believe Iran's claims its nuclear program is strictly peaceful, the IAEA said ahead of a June 14 meeting of its 35-nation board of governors.
The United States has called for the IAEA, which has been investigating the Iranian program since February 2003 after being alerted to it in August 2002, to refer the Islamic Republic to the UN Security Council for possible international sanctions.
But ElBaradei told a NATO meeting in the Slovak capital Bratislava Tuesday "the jury is still out" on Iran's nuclear program.
He said there was at this time "no evidence that the Iranian program has some military dimension."
Diplomats said the IAEA will not be able to reach a decision on Iran in June since Tehran has delayed inspections and only last month submitted a report on its program which the agency will need months to evaluate.
ElBaradei's report praised the Iranians for "cooperating in providing access to locations in response to agency requests, including workshops situated at military sites."
But the report also said that three workshops in Iran are continuing to produce centrifuge components despite Tehran's claim that it has suspended uranium enrichment and related activities.
Iran has said that it had suspended production of centrifuge components as of April 9 as a confidence-building measure with the international community.
But Iran is determined to resume production of uranium hexafluoride (UF6), a feed material for enriching uranium, the report said.
"The Iranians don't seem to be taking suspension seriously," Albright said.
Iran had agreed to the suspension last October in striking an agreement on cooperation with the European big three -- Britain, France and Germany.
Albright said that if Iran "continues to embarrass" these countries by hiding aspects of its program, Tehran may lose their support, and perhaps by December be taken to the Security Council by the IAEA board.