New York: Top scientists had cast doubts over claims that the aluminium tubes found in Iraq were meant for making nuclear weapons, over a year before the Bush administration used their presence to build up the case for invading that country, senior officials were quoted as saying.

In a revelation that could damage President George W Bush's re-election bid on the Iraq war platform, 'New York Times' reported that senior nuclear scientists as early as in 2001 had informed officials that the aluminium tubes could be meant for small artillery rockets.

However, the administration did not pay heed to this advise and went ahead with its plan to invade Iraq, the daily reported quoting four officials of the Central Intelligence Agency (CIA) and two senior administration officials.

Senior members of the administration, including Vice President Dick Cheney, gave a series of speeches and interviews in the run up to the invasion in early 2002, asserting that Iraq President Saddam Hussein was rebuilding his nuclear weapons programme.

The tubes, made of high-strength aluminium, were "only really suited for nuclear weapons programmes," National Security Advisor Condoleeza Rice had said months after the invasion. "We don't want the smoking gun to be a mushroom cloud," she had said.

But almost a year before that, scientists had informed Rice's staff that they seriously doubted the tubes were for nuclear weapons. The White House, though, embraced the disputed theory that the tubes were for nuclear centrifuges, an idea first presented in April 2001 by a junior analyst at the CIA.

Senior administration officials, the report said, repeatedly failed to fully disclose the contrary views raised by America's leading nuclear scientists, the 'Times' said.

They sometimes overstated even the most dire intelligence assessments of the tubes, yet minimised or rejected the strong doubts of nuclear experts.

They worried privately that the nuclear case was weak, but expressed sober certitude in public, the 'Times' said.

One result was a largely one-sided presentation to the public that did not convey the depth of evidence and argument against the administration's most tangible proof of a revived nuclear weapons programme in Iraq.

Now, more than 18 months after the invasion of Iraq, US investigators have not yet found evidence of hidden centrifuges or a revived nuclear weapons programme.