"We expect serious results by the end of the year, but the launch itself will not take place," Russian Energy Minister Sergei Shmatko was quoted by the BBC as saying. "The engineers have to reach their findings."
The plant at Bushehr in southern Iran was due to go online by the end of this year.
The minister said the plant's construction at Bushehr in southern Iran "is defined absolutely 100 percent by technological conditions," but observers believe the delay is due to the stalemate in the conflict over Iran's alleged nuclear weapons program.
The International Atomic Energy Agency, the U.N. nuclear watchdog, Monday issued a report critical of Iran after officials there in September unveiled a previously secret enrichment site that is being built around 20 miles north of Qom.
The revelation increased doubts that there are no more other secret sites, the IAEA said, "and gives rise to questions about whether there were any other nuclear facilities in Iran which had not been declared."
Russia and the United States over the weekend warned Iran not to ignore a recent compromise proposal that would keep negotiations running.
U.S. President Barack Obama said in Singapore that he was unhappy about Iran's seeming unwillingness to agree to a plan drafted by the West aimed at removing concerns that the Iranian civil nuclear energy program was a cover to make nuclear weapons.
Russian President Dmitry Medvedev, after talks with Obama on Sunday, urged Iran to accept an offer to have its uranium enriched in Russia and France or face further diplomatic consequences.
Backed by the consent of Washington, Moscow and Paris, the United Nations has put forward a proposal to have a major share of Iran's low-level uranium sent to Russia for processing. The processed uranium would then go to France, where the country's nuclear industry would convert it into fuel rods for use in Iranian reactors. However, Tehran has missed a deadline to respond to the proposal.
Obama after the start of his presidency offered Iran direct negotiations regarding its nuclear program; he has previously said that Tehran needed to prove it is willing to find a compromise in the conflict by the end of the year.
The Bushehr plant will feature two pressurized water reactors and is estimated to cost around $1 billion. The uranium used there will be imported from Russia and also returned there to make sure it is not used to build a nuclear weapon.
Work at the facility was begun in 1974 with German aid, but the project was terminated after the Islamic revolution of 1979.