Russia is urging Iran to abide by a resolution adopted by the International Atomic Energy Agency giving Tehran until the end of October to prove it has no plans for developing nuclear weapons.
Deputy Foreign Minister Sergei Kislyak says Iran should respect the resolution by the IAEA's board of governors, even though it is not a firm ultimatum.
The resolution, adopted Friday, gives Iran until October 31 to prove that it does not seek to develop nuclear weapons, as many countries suspect.
Mr. Kislyak says the resolution aims to resolve any questions the agency has about what he calls Iran's "peaceful nuclear programs." His choice of words appeared aimed at soothing Iran, which has hinted it may stop cooperating with the U.N. nuclear watchdog agency.
The Iranian ambassador walked out of the Vienna headquarters of the atomic energy agency during Friday's meeting. He called the deadline "illegitimate, illegal and impractical."
Russia is building a nuclear power plant at Bushehr in southern Iran. Russia has rejected calls to halt work on the $800 million plant, which has been under development for 10 years.
The United States and other countries are concerned it could be used in a secret weapons program.
Russia has itself come under pressure over an issue that has been the subject of discussion at meetings between Russian President Vladimir Putin and President Bush.
Russia has also had problems dealing with Tehran over the plant's construction. The two countries have so far failed to reach an agreement on what will happen to spent nuclear fuel generated by the power plant.
Moscow has refused to send nuclear fuel for the plant, until Iran agrees to return all spent fuel to Russia.
Critics say Iranian engineers could easily use the fuel for a weapons program. They also question the need for Iran to develop nuclear energy, as it is one of the world's leading exporters of oil.