France and Australia also questioned Iran's claim that it had acquired an industrial-scale nuclear fuel production capability, and the European Union urged Tehran to live up to international demands that it halt its nuclear program and return to negotiations.
Iran said Monday it has begun operating 3,000 centrifuges — nearly 10 times the previously known number — in defiance of U.N. demands that it halt its nuclear program or face increased sanctions. The United States, Britain, France and others criticized the announcement.
Russian Foreign Ministry spokesman Mikhail Kamynin said in a statement, however, that Moscow was unaware of "any recent technological breakthroughs in the Iranian nuclear program that would change the format of its enrichment effort."
Russia, which has close economic ties with Iran, is building its first nuclear power plant in the southern port of Bushehr. But Moscow delayed Bushehr's planned September launch, and last month refused to ship uranium fuel for the reactor, citing Iran's payment arrears. Iranian officials denied any payment delays, and accused Russia of caving in to Western pressure.
Moscow has asked International Atomic Energy Agency, or IAEA, for its assessment of the Iranian claim, but Russian Foreign Minister Sergey Lavrov said Tuesday he had yet to receive a response.
"We haven't got confirmation yet that they have actually begun uranium enrichment at the new cascades" of centrifuges, Lavrov told reporters.
Iran's statements "require clarification," said President Vladimir Putin's foreign policy adviser, Sergei Prikhodko, adding that Russia would rely on the IAEA for that.
He expressed regret that Iran "does not always heed" Moscow's advice and that its suggestions to Tehran of ways to resolve the confrontation "are not finding the appropriate reaction," reflecting persistent Russian frustration with Tehran's recalcitrance.
French Foreign Ministry spokesman Jean-Baptiste Mattei also questioned the Iranian claim, saying: "there are announcements, and then there is technological reality."
Australian Foreign Minister Alexander Downer voiced similar doubts about Iran's ability to produce substantial quantities of enriched uranium. "I'm not sure if that is true or not," he said.
Russia and China last month joined the rest of the U.N. Security Council in voting to impose the new sanctions against Tehran — the second set in three months — for its refusal to suspend uranium enrichment. The sanctions included a ban on Iranian arms exports and an asset freeze against 28 people and organizations involved in Iran's nuclear and missile programs.
Iran rejected the sanctions and announced a partial suspension of cooperation with the IAEA.
The 27-nation EU and the United States fear Iran's enrichment program is being used to develop nuclear weapons, while Iran insists it seeks only to generate electricity.
"Iran should comply to its obligations under the Nuclear Nonproliferation Treaty," EU spokeswoman Christiane Hohmann said.
In the enrichment process, uranium hexafluoride gas is pumped into centrifuges, which spin and separate the fissionable uranium isotopes from molecules containing nonfissionable isotopes. Enriched to a low degree, the result is fuel for a reactor, but to a high degree it creates material for a nuclear warhead.
U.S. experts say 3,000 centrifuges are, in theory, enough to produce a nuclear weapon, perhaps within a year. But they doubted Iran had so many operational, a difficult technical feat given the country's patchy success with a much smaller number.
Iran's President Mahmoud Ahmadinejad claimed Monday that his nation had "joined the nuclear club of nations and can produce nuclear fuel on an industrial scale" — comments suggesting Iran was able to produce enough enriched uranium to fuel a nuclear reactor consistently. Vice President Gholamreza Aghazadeh said Iran would install 50,000 centrifuges.
"We have heard the Iranian president's statement and have adopted a serious attitude to what is going on in relation to the Iranian nuclear program," Lavrov said Tuesday. "But we would like to proceed from facts, not from emotional political gestures."
The Russian Foreign Ministry spokesman urged Tehran to cooperate with the IAEA. "Iran's threat to walk out of the Nuclear Nonproliferation Treaty has caused a particular concern," Kamynin said Tuesday.