The US Congress has ordered an investigation into possible abuse of intelligence information about alleged weapons of mass destruction in Iraq.
This is the first serious domestic pressure on the Bush administration
The inquiries, launched by both Republican and Democratic politicians, will include public hearings that will be televised live.
The CIA is reported to be prepared to co-operate fully.
This is the first serious domestic pressure on the Bush administration to give a detailed explanation of its pre-war claims about weapons of mass destruction.
The announcement came the day that Hans Blix - the man the UN appointed to find out whether Iraq still possesses weapons of mass destruction (WMD) - submitted what is likely to be his last report to the Security Council before leaving the post.
The inquiries are to be conducted by the Senate Armed Services and Intelligence Committees.
They are expected to hold a joint public hearing later in the month.
Henry Waxman, a California Democrat on the House Government Reform Committee, called on Mr Bush to explain why the administration cited dubious and later discredited documents to back its claims about Iraqi weapons.
"To date, you have offered no explanation as to why you and your most senior advisers made repeated allegations based on forged
documents," Mr Waxman said in a letter to the president.
Senator John Warner, the Republican chairman of the armed services panel, said he had ordered the inquiry because of the depth and seriousness of the issue.
"The situation is becoming one where the credibility of the administration and Congress is being challenged," he said.
Mr Warner said he had been assured by CIA director George Tenet that all the statements made by the administration on the subject and all the intelligence supporting those statements would be supplied to the committee.
It is likely that senior officials such as Defence Secretary Donald Rumsfeld and Secretary of State Colin Powell will be summoned before Congress.
On Monday the administration defended the intelligence it presented to justify the war against Iraq.
Mr Powell, speaking in Rome, said he thought the evidence that Iraq had continued to develop weapons of mass destruction was "overwhelming".
In a 40-page report submitted on Monday, chief UN weapons inspector Hans Blix presented no definitive answer about whether Iraq still possessed WMD, but outlined unanswered questions on the issue.
UN weapons inspectors - who returned to Iraq last November after a four-year absence - had to leave the country again in March ahead of the US-led military campaign