"We are very alarmed, and we cannot accept that Iran is refusing to cooperate" with the global nuclear oversight body, the International Atomic Energy Agency, Lavrov said on Ekho Moskvy radio.

The IAEA on Thursday issued a report saying Iran may currently be working on making a nuclear warhead, suggesting for the first time that the Islamic Republic had either resumed such work or never stopped in 2003 as a U.S. intelligence assessment published three years ago said.

Iran's Supreme Leader Ayatollah Ali Khamenei on Friday denied that Tehran was seeking nuclear weapons, saying Islam forbids weapons of mass destruction.

But Lavrov said he did not understand the need for Iran to conduct its nuclear program in secret, withholding information from the IAEA.

Susan Rice, the U.S. ambassador to the United Nations, said the IAEA report "underscores that Iran continues to flout its international obligations" and indicates that Tehran is pursuing "a nuclear weapons program with the purpose of evasion."

The United States has circulated elements for a possible new U.N. sanctions resolution to other veto-wielding U.N. Security Council members — Russia, China, Britain and France — and Germany. The six countries have been trying, to no avail, to get Iran to suspend its uranium enrichment program and return to negotiations on its nuclear program.

Rice told reporters at U.N. headquarters in New York that the report also demonstrates "the urgency" that Iran must now engage the international community on its nuclear program or "face increased international pressure."

The French Foreign Ministry went further in a statement Friday, saying the IAEA report "shows how urgent it is to take resolute action to respond to Iran's lack of cooperation."

"We now have no other choice, given this report, than to seek, together with our partners, the adoption of new measures by the U.N. Security Council over the next few weeks," the ministry said in a statement.

The United States and its Western allies have been pushing for a fourth round of U.N. sanctions. But with China, which relies on Iran for much of its energy, skeptical of any new sanctions, they have to tread carefully to maintain six power unity on how to deal with Iran.