Meanwhile, the Islamic Republic's envoy to the United Nations atomic watchdog dismissed as "baseless" a leaked report expressing concern that it may have been trying to develop a nuclear warhead, the Fars news agency reported.
Ali Asghar Soltanieh said the documents cited in the report by the International Atomic Energy Agency were "fabricated and thus do not have any validity."
"I have also said many times that when they showed these documents to us none of the documents had any confidential or secret stamps on them," Soltanieh said.
"And thus it was proved that all of the documents have been fabricated and are baseless and thus do not have any validity.
"The issue of the missile or explosives has nothing to do with the IAEA's charter and function," he added.
Russian Foreign Ministry spokesman Andrei Nesterenko was quoted as saying at a briefing in Moscow, "Tehran must be more active in its cooperation with the IAEA and widen it."
The comments reinforce indications that Moscow's patience with Tehran is wearing thin and the Kremlin is aligning itself more closely with Western demands for UN sanctions.
The United States is leading a push for the UN Security Council to impose a fourth round of sanctions.
Nesterenko said Tehran should also provide information to dispel suspicions about the character of its nuclear program, Russian news agencies reported. "The international community needs to know for certain that it is peaceful," he said.
Peres: Iranian regime a group of executioners
The UN nuclear watchdog said in a confidential report obtained by Reuters on Thursday that it feared Iran may be working now to develop a nuclear payload for a missile.
The report also confirmed Iran had produced its first, small batch of uranium enriched to a higher purity – 20% - but said the Islamic Republic had failed to give inspectors the required advance notice.
"The information available to the agency is extensive ... broadly consistent and credible in terms of the technical detail, the time frame in which the activities were conducted and the people and organizations involved," the report said.
Peres at Conference of Presidents (Photo: Avi Hayun)
The language of the report was much more blunt than that used by Amano's Egyptian predecessor Mohamed ElBaradei, who stepped down at the end of November.
The Vienna-based IAEA has been investigating for a number of years intelligence reports claiming Iran was involved in weapons research.
A US intelligence report in 2007 said Iran halted such research in 2003, but Amano's report gives credence to the belief of some Western governments that the program has covertly continued.
President Shimon Peres on Friday criticized the Iranian regime, calling it "a group of executioners trying to find a bomb."
Peres told the Conference of Presidents of Major American Jewish Organizations in Jerusalem that "the problem is not with the bomb, but with the nature of the regime trying to obtain it."
AFP, Reuters and Ronen Medzini contributed to this report