Bush said on Monday he will appoint an independent commission to investigate discrepancies in intelligence used to justify the war against Iraq.
"I want to know all the facts," he told reporters. He also said he would meet soon with David Kay, the former chief US weapons hunter in Iraq, who told a congressional hearing last
week that much of the intelligence about Iraq's alleged weapons of mass destruction was wrong.
Bush, who had earlier opposed such a commission, was under strong pressure from Republicans and Democrats in Congress to support an independent, bipartisan probe into intelligence.
Intelligence reports presented by the White House claimed Iraq possessed chemical and biological weapons ready for imminent use when in fact none has been found.
British Prime Minister Tony Blair's government said on Monday it would announce shortly whether it would follow the US and open a similar inquiry.
Britain's premier has refused to
investigate intelligence failures
After Bush's announcement, Blair is under intense pressure to do the same and to explain why no such banned arms have yet been uncovered.
Blair, to a much greater extent than Bush, cited Saddam Hussein's refusal to give up his pursuit of banned weapons as the main reason for taking Britain into the US-led Iraq campaign last March.
Michael Howard, head of Britain's opposition Conservative Party, was to put forward a parliamentary motion demanding a probe into the quality of data on Saddam Hussein's alleged weapons of mass destruction.
"Everybody, I think, now recognises that something went wrong over the intelligence," Howard said in a ITV television interview.
On Tuesday, Blair faces a potentially difficult grilling when he makes a regular appearance before a parliamentary committee of senior lawmakers.
In Sydney, Australian Prime Minister John Howard, an avid supporter of the war, also came under renewed pressure to order an inquiry into the intelligence used to justify the invasion, but Howard has rebuffed the demand.
Up to now, Bush too had dodged growing calls for an independent probe, saying US inspectors should finish their work and insisting the invasion that toppled Saddam Hussein had removed a "danger" to the United States and the world.
But pressure has piled on since former chief US arms inspector David Kay resigned and told US lawmakers last week that he believed Iraq did not possess chemical, biological or nuclear weapons.
Kay said massive intelligence failures led to the mistaken belief Iraq had such arms in violation of UN sanctions, calling for an independent investigation.