"The prime minister believes, and is absolutely confident, that we will find material" relating to chemical, biological and nuclear weapons, a spokesman for Blair told reporters.

"The prime minister is also absolutely confident that we will find evidence not only of his WMD programmes, but concrete evidence of the product of those programmes as well," he added.

Blair's defensive stance came amid controversy in both London and Washington over the way in which both capitals made the case for ending UN arms inspections and launching the March 20 invasion to topple the Iraqi leader Saddam Hussein.

Blair had suggested Tuesday that only "evidence of programmes" would likely be uncovered. But the spokesman on Thursday made clear the prime minister also expected actual weapons to be found.

The BBC -- which in late May reported that a British government dossier on Iraq in September was "sexed up" to help justify military action -- quoted unnamed senior government officials Wednesday as saying they no longer believed weapons of mass destruction will be uncovered in Iraq.

"Senior government sources are telling me that they no longer believe that physical weapons of mass destruction are actually going to be found in Iraq," the BBC's respected political editor Andrew Marr reported.

"They don't think that there were no weapons programmes. They believe that interviews with Iraqi scientists, perhaps documentation will be uncovered which will reveal the extent of programmes that were then in the past."

"But when it comes to physical evidence I have to say that the belief that that will be found and can be paraded in front of the cameras seems to be trickling into the sand," Marr said on BBC television.

Robin Cook, who quit Blair's cabinet in protest over the war, said Thursday the government would have to display Iraq weapons of mass destruction to vindicate Britain's decision to go to war.

The government "said quite explicitly that there were weapons, indeed famously they said there were weapons that would be ready within 45 minutes", Cook told BBC radio.

"They also said that Saddam had rebuilt the factories to make more chemical weapons. To establish that that is correct, you do have to produce the weapons. You do have to actually produce the factories," he added.

"You cannot now say 'well, there were some scientists around who might at some time have had a capacity to develop it'. That is not what (Britain's) parliament was being told in March when it voted for war."

Meanwhile, the BBC was under pressure to reveal the source who alleged that the government's September dossier on Iraq was "sexed up", against the wishes of intelligence chiefs, by inserting the claim that Saddam could deploy chemical or biological weapons within 45 minutes.

Britain's defence ministry Wednesday named the source they believed responsible -- one David Kelly, a government adviser on weapons of mass destruction.

"We have to assume that this is their source," Blair's spokesman said.

WAR.WIRE