"I have no reason to believe that the situation will change from its current course and that the character of Iran's nuclear program will change," Interfax quoted Foreign Minister Sergei Lavrov as saying on a visit to the northwestern town of Petrozavodsk.

"Russia and Iran are leading a detailed dialogue, so that Iran's nuclear program remains exclusively peaceful in nature," Ivanov said.

Russia is completing construction of Iran's first nuclear power reactor despite fears in the United States and Israel that the project could help the Islamic state develop nuclear warheads.

Moscow has refused to supply nuclear fuel to the Bushehr plant until it wins a formal, written assurance from Iran that it would return all spent fuel for storage back to Russia -- a guarantee that Tehran has so far failed to provide.

The material could theoretically be reprocessed through high-tech technology to make weapons-grade nuclear material.

Bush, speaking to NBC television on Monday, said he would not rule out military action if the United States cannot persuade Iran to stop short of building a nuclear weapon.

"I hope we can solve it diplomatically, but I won't ever take any option off the table," Bush told NBC.

But Lavrov replied for Russia: "It is premature to talk before one has facts."

The president was quizzed about Iran as The New Yorker magazine reported that US commandos have been operating inside Iran since mid-2004 selecting suspected weapons sites for possible air strikes.

The Pentagon blasted the article as "riddled with errors."