The United States and more than a dozen allies have pushed the UN nuclear watchdog to back a resolution that will give Tehran until October 31 to prove it has no clandestine nuclear weapons programme.
Japan, Turkey, Britain, France and Germany joined forces with Washington and nine other nations by co-sponsoring a draft that demanded Iran demonstrate full compliance with the nuclear Non-Proliferation Treaty (NPT), which the United States says Tehran has violated to secretly develop atomic weapons.
The toughly-worded draft resolution, expected to be voted on at Thursday's closed-door meeting of the International Atomic Energy Agency's (IAEA) 35-nation Board of Governors, also called on Iran to "suspend all further uranium enrichment activities".
Iran's foreign minister warned that the Islamic republic, which denies having atomic weapons ambitions, would "review" cooperation with the UN watchdog body if its governing board came down too hard on Tehran.
Ali Akbar Salehi, Iran's ambassador to the IAEA, said the decision of France and Germany to co-sponsor the resolution was clearly an attempt to ingratiate themselves with Washington after refusing to back the US-led war on Iraq.
"They are now taking Iran as a scapegoat to bring themselves together," he said, rejecting the idea of a deadline.
IAEA chief Mohamed ElBaradei appeared to support the US-backed resolution when he spoke to the board today, a diplomat told journalists.
"If we're not getting immediate and full cooperation (from Iran), we might not be able to verify non-diversion," the diplomat quoted ElBaradei as saying at the closed door meeting.
If the IAEA board decided the agency was unable to verify "non-diversion" of nuclear resources to a weapons programme - as it did with North Korea in February - it would have to report Iran to the UN Security Council for possible economic and diplomatic sanctions.
"I would like to come to a conclusion (about the nature of Iran's nuclear programme) by the next board meeting," ElBaradei said. The IAEA board is due to meet again in November.