"Our concerns regarding Iran's pursuit of nuclear weapons are well known and still stand," said White House national security spokesman Sean McCormack. "They need to come clean and comply with all their international obligations.

Washington has long insisted that oil-rich Iran has no legitimate use for a civilian nuclear power program, alleging that the Islamic republic instead seeks atomic weapons.

McCormack had no comment on reports that the United States seeks a deadline for Iran's compliance with the International Atomic Energy Agency, but State Department spokesman Richard Boucher said Washington wants the UN agency to pass a resolution this week demanding Tehran cooperate with inspectors.

"The US believes the board of governors this week must adopt a strong resolution that calls on Iran to cooperate with the IAEA and to resolve all the outstanding issues regarding its nuclear program," Boucher said.

"At this point we think it is the appropriate step."

Earlier, IAEA chief Mohamed ElBaradei said it was important his agency's probe of Iran's suspected nuclear weapons program be completed within a few months and that Tehran had to do more to cooperate.

"It is essential for the integrity and credibility of the inspection process that we are able to bring these issues to a close within the next few months and provide the international community with the assurances it urgently seeks regarding Iran's nuclear activities," ElBaradei told the UN agency's board.

"The central question is whether Iran's uranium enrichment activities have been fully declared," ElBaradei said, according to a copy of his speech to the 35-nation board meeting in Vienna.

ElBaradei said the IAEA has been aware of Iran's undeclared nuclear program for almost two years but had been kept from getting to the bottom of it due to "less than satisfactory" cooperation from Tehran.

Tehran needed to be "proactive and fully transparent" from now on as "we can not go on forever," ElBaradei said.

The United States accused Iran of secretly trying to develop nuclear weapons, of which uranium enrichment is a crucial stage, and said it should be taken to the UN Security Council for possible sanctions.

But Washington does not have support at the IAEA for its hardline stance.

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