"It is a clear U-turn. It is an evolution within the US administration. It marks a stepping back" on the part of the White House, Ahmadinejad told state television in an interview.

The National Intelligence Estimate -- the consensus view of all 16 US spy agencies -- said Iran had halted a nuclear weapons programme in 2003, whereas the White House had previously accused Tehran of continuing an active atomic weapons drive.

Ahmadinejad said that the "fact they say that Iran has not deviated over its nuclear programme" deserves a "bravo."

He said last week that the report was a "positive step," adding that more moves from Washington could end decades of enmity between the foes. But the White House said it was up to Iran to make nuclear concessions first.

Western powers, led by the United States, are still pushing for a third UN sanctions resolution against Tehran to punish its defiance in the nuclear standoff.

But Ahmadinejad said that a new resolution against Iran was "out of the question."

Iran has repeatedly refused to cede to the key demand of the West that it suspend uranium enrichment work, a potential nuclear weapons-making process, despite already having been slapped with two sets of UN sanctions.