The United States confirmed Thursday it will press for a referral of Iran's nuclear program to the U.N. Security Council for possible sanctions against Tehran. The International Atomic Energy Agency (IAEA) begins a critical meeting on Iranian compliance with nuclear agreements September 13 in Vienna.

U.S. officials had been sending mixed signals about the Bush administration's intentions with regard to the upcoming meeting of the IAEA governing board. But in a talk with reporters on a flight from Panama late Wednesday, Secretary of State Colin Powell said flatly for the first time that the United States will press in Vienna for a referral of the matter to the Security Council.

The Powell remarks follow the release Wednesday of a report by IAEA inspectors revealing that despite earlier commitments to key European foreign ministers, Iran intends to pursue the further enrichment of some 37 tons of so-called yellowcake uranium, and to continue work on centrifuges that could produce weapons-grade uranium.

The report, the latest in a series by the IAEA staff, made no conclusion as to whether Iran is actually pursuing a nuclear weapons program, but said they had been unable to clear up suspicions and questions about Iranian activities.

While Iran insists its nuclear program is entirely peaceful, the United States has long maintained that it conceals a clandestine weapons project.

At a news briefing, State Department Spokesman Richard Boucher said Iranian non-compliance with the IAEA is amply demonstrated in the new report and those that preceded it, and that it is time for the U.N. agency to move the matter to the Security Council.

"We think it's time on Iran for the board to take appropriate action," he said. "We've got six reports on Iran, six reports from the [IAEA] director-general on Iran that detail an 18-year history of non-compliance, that detail new efforts by Iran, and plans by Iran not to comply. It's time."

Secretary Powell said in his airborne interview late Wednesday that it remained to be seen whether there will be a consensus on the 35-nation board to refer the case to the Security Council, but said from the U.S. point of view "we think we've seen enough."

He said he would be personally contacting the foreign ministers of Britain, France and Germany, who have visited Tehran to press for full disclosure, and other member countries of the IAEA board to try to generate the necessary support for referral.

Iran has already dismissed the U.S. diplomatic effort, saying the latest U.N. report has failed to prove Washington's charges. It has threatened in the past to cease cooperation with the IAEA if a Security Council referral was made.