The announcement was a tacit rebuff to a deal brokered by Brazil and Turkey and made public on Monday in which Iran agreed to send some uranium abroad. U.S. officials regard that deal as a maneuver by Iran to delay more U.N. sanctions.

"This announcement is as convincing an answer to the efforts undertaken in Tehran in the last few days as any that we could provide," Clinton added, repeating that Washington has many questions about the fuel swap deal.

The deal had revived the idea of a nuclear fuel swap devised by the United Nations last year with the aim of keeping Tehran's nuclear activities in check.

But Tehran made clear it did not intend to suspend domestic uranium enrichment that Western governments have said appears aimed at giving it the means to make nuclear weapons.

Western nations have reacted skeptically to the deal, although China -- the major power most reluctant to impose more sanctions on Iran -- welcomed it and urged talks with Tehran.

Clinton told lawmakers in Washington: "We have reached agreement on a strong draft with the cooperation of both Russia and China." She gave no details of the draft, but said it would be circulated to the full Security Council later on Tuesday.

She said the agreement was reached among the five permanent Security Council members -- Britain, China, France, Russia and the United States -- and Germany, which have been engaged in talks on ways to address any nuclear threat from Tehran.

The Security Council will hold a closed-door session on Tuesday afternoon to receive the draft, diplomats said, and the United States is looking to get the maximum backing in the 15-member council.

Washington…Secretary of State Hillary Rodham told a Senate committee that U.S. officials have reached agreement with council members China, Russia, Great Britain and France for a draft sanctions resolution that will be sent to the full 15 member council later Tuesday.

The announcement to the Senate Foreign Relations Committee came one day after Iran offered a diplomatic proposal that many Western leaders view as an attempt to deflect the new round of economic strictures.

"This announcement is as convincing an answer to the efforts undertaken by Tehran over the last few days as any we could provide," Clinton said.

Germany, a close ally though not a council member, also agreed on the draft.

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Clinton said that while the United States acknowledges the efforts of Brazil and Turkey to assist with the new Iranian offer, "we are proceeding to rally the international community on behalf of a strong sanctions resolution that will in our view send an unmistakable message about what is expected from Iran," Clinton said.

She said the Iranian proposal, under which Tehran would temporarily shift about half of its low enriched uranium abroad, leaves "a number of unanswered questions."

Clinton emphasized that Russia and China, who have been long resistant to sanctions, had agreed on the new proposal.

Even so, Russian and Chinese views on how quickly to push for adoption was not immediately clear.

Chinese officials on Monday hailed the Iranian proposal, and said it should be fully explored.

US officials have been openly predicting in recent days that they would complete the initial negotiations this week. They have forecast that the full council might act in June.

Many world powers believe that Iran has been secretly working to acquire bomb making know how. Iran insists that its goal is entirely peaceful.