Updated

WASHINGTON -- Secretary of State Hillary Rodham Clinton said Tuesday the United States has agreed with China, Russia and other major powers on a proposal for "strong" new sanctions against Iran's nuclear program.

Clinton told a Senate committee that the five permanent members of the Security Council -- Britain, China, France, Russia and the U.S. -- along with Germany would send a new draft sanctions resolution to the entire council later Tuesday, capping months of painstaking negotiations.

Clinton said she spent Tuesday morning on the phone with Russian Foreign Minister Sergey Lavrov "finalizing the resolution," which will be introduced in the United Nations later in the day. Details were not immediately released, but the sanctions are expected to broaden economic penalties on Iranian officials and institutions.

Russia in China have previously resisted calls for a new round of sanctions, but in recent months have been persuaded they were needed.

The announcement came just a day after Iran, Brazil and Turkey said they had agreed on a confidence-building plan for Iran to swap nuclear materials that many believed would blunt the U.S.-led drive for a fourth round of U.N penalties on Iran.

Clinton said the agreement on a new resolution by the major powers was a rejection of Iran's efforts to forestall penalties.

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

U.S. and European officials had reacted skeptically to the Brazilian-Turkish-brokered proposal, warning it still allows Iran to keep enriching uranium toward the pursuit of a nuclear weapon. The deal was concluded during a visit to Tehran by Brazil's President Luiz Inacio Lula da Silva who has fought against a new round of sanctions.

Clinton repeated the U.S. skepticism about the agreement, saying "there are a number of unanswered questions regarding the announcement coming from Tehran."

"While we acknowledge the sincere efforts of both Turkey and Brazil to find a solution regarding Iran's standoff with the international community over its nuclear program, 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 did not disclose details of the draft, which will be presented to the entire 15-member U.N. Security Council at 4 p.m. (2000 GMT) Tuesday, U.N. diplomats said, speaking on condition of anonymity ahead of an official announcement.