But this time moderates in the administration are likely to put up tougher opposition to military action against Iran or covert support for Iranian opposition groups, officials say.

President Bush, in an interview broadcast on Russia's Rossiya television channel on Friday, said reports of US plans to attack Iran were "pure speculation."

"We've had all kinds of reports that we're going to use force against Syria and now some on the left, I guess, are saying force in Iran or force here and force there. You know, it's pure speculation," said Bush, who denied for months that the United States had any plans to attack Iraq.

ABC News said this week the Defence Department was advocating a massive covert action program to overthrow the Iranian government as the only way to stop the country's nuclear program, which Washington says is for making bombs.

A State Department official, who asked not to be named, said Defence Department hawks and allies in Washington's neoconservative think tanks had not presented any formal plans but were encouraging such speculation in leaks to the media.

AFP adds: The United States would like to see a different kind of regime in Iran, which will move away from "pursuing an aggressive agenda based on terrorism and weapons of mass destruction", Condoleezza Rice, national security adviser to US President George W. Bush, told Saturday's Financial Times.

But Rice's statement of US ambitions in an interview with the paper fell short of the desire for regime change in Tehran, the London-based business daily said.