In the lead-up to the war, Australia and the United States cited the seizure of 60,000 Iraq-bound aluminium tubes in Jordan in May 2001 as evidence Saddam Hussein was amassing equipment for a nuclear program.

Early Tuesday, Foreign Minister Alexander Downer said Canberra toned down its claims the tubes were part of a centrifuge to manufacture enriched uranium in early 2003, soon after receiving a US State Department report dated October 2002 raising doubts about the theory.

"In relation to the aluminium tubes there was some debate about that and that is why we were reasonably circumspect in how we articulated the information about the tubes," he told ABC radio.

Later in the day, he said the government began qualifying references to the tubes in September 2002 and said the government had been "completely honest and up-front" about the tubes' potential nuclear applications.

Downer told parliament in September 2002 that Australian intelligence believed Iraq was gathering equipment for a nuclear weapons program and Baghdad's attempt to buy "very specific types of aluminium tubes may be part of that pattern".

"Saddam Hussein could build a nuclear bomb within months if he were able to obtain fissile material", Downer said at the time.

Former US State Department intelligence officer Greg Thielman told ABC television in a program aired Monday that Australia and other US allies knew it was doubtful the tubes were part of a nuclear program.

"The Australians knew about the dissenting positions of theintelligence bureau, the State Department and the Department of Energy," Thielman said.

"There was no change, no apparent change in the position of the CIA. They were unfazed by all the contrary evidence, which surprised me greatly."

Opposition foreign affairs spokesman Kevin Rudd said it was clear Canberra knew the tubes were not part of a nuclear program months before Prime Minister John Howard's administration stopped using them as a reason to justify the war.

"This once again is the Howard government being loose with the truth on national security," he told reporters.

Greens senator Bob Brown said Howard should apologise for "deceiving" Australians by failing to tell them that claims about the tubes' nuclear potential were dubious "if not downright wrong".

"They knew the aluminium tubes affair had a hollow ring to it but they weren't about to tell Australia in the lead-up to the Iraq war," he said.

Downer, however, said Iraqi scientists captured during the war had confirmed Saddam Hussein was firmly committed to developing nuclear weapons and "the nuclear program wasn't just about the aluminium tubes".

Asked whether the government should have omitted evidence subject to so many doubts from its case for war with Iraq, Downer replied: "Absolutely not".

Weapons experts now believe the tubes were probably intended for use as artillery rocket casings.

A pre-war claim that Iraq was attempting to buy uranium yellowcake from Africa for its nuclear program has also been discredited in recent months.

WAR.WIRE