British Prime Minister Tony Blair said yesterday that history would forgive America and Britain for invading Iraq, even if they were proved wrong about the threat from its weapons of mass destruction.

In an impassioned defense of the war, Mr Blair told a joint meeting of the US Congress that toppling former Iraqi President Saddam Hussein was justified irrespective of the suspected armament that has failed to materialise.

"Can we be sure that terrorism and WMD will join together? Let us say one thing: If we are wrong we will have destroyed a threat that at its least is responsible for inhuman carnage and suffering," Mr Blair said in what was billed as one of the most important foreign speeches of his six-year premiership.

"That is something I am confident history will forgive." Mr Blair and US President George W. Bush are under fire for allegedly hyping up the threat from Iraq's weapons - their primary motive for the war - to justify the conflict.

What should have been a period of triumph after a swift military campaign has turned into a nightmare for the allies.

Political chaos grips parts of Iraq, troops are under attack and public trust in Mr Blair has slumped while Mr Bush's approval ratings have slipped since the war ended.

Mr Blair was due to meet Mr Bush after his speech to Congress in a meeting meant to reinforce a special relationship that has been strained recently by controversy over whether disputed British intelligence on Iraq's alleged nuclear programme was used by Mr Bush as an excuse to attack Saddam.

Mr Blair remained adamant over the justification for war. "But if our critics are wrong, if we are right, as I believe with every fibre and instinct of conviction I have that we are, and we do not act, then we will have hesitated in the face of this menace when we should have given leadership, that is something history will not forgive," he said.

Becoming only the fourth British prime minister to address a joint meeting of the US Congress, Mr Blair also sought to deflect criticism that he was "Bush's poodle."

He said the US must remain committed to the reconstruction of Iraq and to the Middle East peace process, which he said was crucial to the fight against terrorism. He made a brief mention of the Kyoto protocol on greenhouse gas emissions, which Mr Bush pulled out of, and asked Mr Bush not to "give up on Europe."

"America must listen as well as lead," Mr Blair said, adding: "But don't ever apologise for your values."

Later, Mr Blair was due to press Mr Bush over US plans to try British terror suspects being held at the US military base in Guantanamo Bay in Cuba in military courts.

The issue has caused an uproar in Britain with commentators calling on Mr Blair to prove that he has influence over Mr Bush.

The prison was set up to house Taliban and al Qaeda suspects captured primarily in Afghanistan after the September 11, 2001, attacks on the United States. Inmates can face a possible death sentence. Britain opposes capital punishment.

Earlier, White House spokesman Scott McClellan said the matter of the British detainees was "under discussion."

While Mr Blair continues to face questions about weapons of mass destruction, Mr Bush has come under fierce fire from Democrats over the almost daily deaths of US soldiers in guerrilla attacks in Iraq and his disputed allegation that Saddam tried to buy uranium in Africa.

US officials said they did not expect Bush and Blair to spend much time discussing the intelligence on the Iraq nuclear program that has been discounted by the CIA but adamantly defended by Mr Blair. Nor did they expect the president to ask the prime minister to publicly release the British intelligence.

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