The United States urged Iran on Monday to agree to a meeting with the six key nations trying to ensure that its nuclear program is peaceful in which the U.S. will be "a full participant."

U.S. deputy ambassador Rosemary DiCarlo told the U.N. Security Council that Iran has not responded to the request from the five permanent council members — the U.S., Russia, China, Britain and France — and Germany for new talks, which would be the first international discussion on Iran's nuclear program since President Barack Obama took office in January.

"The United States remains committed to direct diplomacy with Iran to resolve issues of concern to the international community and will engage on the basis of mutual respect," DiCarlo said. "The United States will be a full participant in these discussions and we continue to urge Iran to accept this invitation."

DiCarlo's comments came hours after Mohamed ElBaradei, head of the International Atomic Energy Agency, also urged Iran to "respond to the U.S. initiative with an equal gesture of goodwill and trust-building."

The Security Council met to hear a report by the committee monitoring sanctions against Iran as hundreds of thousands of Iranian protesters supporting reform leader Mir Hossein Mousavi defied the government and streamed through Tehran denouncing President Mahmoud Ahmadinejad's claim to victory in a disputed election.

Iran has been slapped with three rounds of sanctions by the Security Council over suspicions it is hiding nuclear activities and fears that it could retool its enrichment program from making low-grade material to produce nuclear power into producing weapons-grade uranium used for nuclear warheads.

The Iranian government insists that its nuclear program is purely peaceful — but ElBaradei told Monday's meeting of the U.N. agency's 35-nation board that for over a year, Tehran has rebuffed IAEA requests for visits and information "to exclude the possibility of military dimensions to Iran's nuclear program."

Diplomats from Britain, France, Russia and China echoed DiCarlo's call for a quick resumption of negotiations with Iran.

"The international community has made clear our desire for a mature partnership for Iran," Britain's deputy U.N. ambassador Philip Parham said.

"We hope that we will see a genuine response from the Iranian government in the weeks and months ahead, but this opportunity is not a blank check," he said. "We need to make real and urgent progress. ... The offer will not be there forever."

Iran welcomed a "constructive" dialogue with world powers over its nuclear program on April 22, but insisted that it won't halt its uranium enrichment activities. The statement, carried by the official IRNA news agency, came in response to the invitation from the six parties for a new round of nuclear talks — but there has been no official response.

On April 9, Ahmadinejad said Iran would present a new proposal for negotiations, saying "conditions have changed" — an apparent reference to Obama's election and Iran's own progress in its nuclear program since previous international talks were held last year.

The U.S., Britain and France expressed concern at the latest IAEA report which underscored Iran's continued defiance of the Security Council in refusing to suspend uranium enrichment, provide access to all its nuclear facilities, and answer questions about past nuclear activities.

Russia's U.N. Ambassador Vitaly Churkin said it was important that the six countries maintain their commitment to assist the IAEA in establishing that "there are no military aspects" to Iran's nuclear program.