Suicide bombers could crash-land an aircraft packed with high explosives into the Pentagon, the headquarters of the CIA or the White House

September 1999 intelligence report

But the Senate Majority Leader, Tom Daschle, dismissed Mr Bush's defence, accusing him of missing the point.

"I think the question is, why didn't he know? If the information was made available, why was he kept in the dark?" the Democrat politician said.

His comments came as it was revealed that two years before the 11 September attacks, an analysis prepared for US intelligence warned that Osama bin Laden's terrorists could hijack an airliner and fly it into government buildings.

"Suicide bomber(s) belonging to al-Qaeda's Martyrdom Battalion could crash-land an aircraft packed with high explosives (C-4 and semtex) into the Pentagon, the headquarters of the Central Intelligence Agency (CIA), or the White House," the September 1999 report said.

No alarm

The Bush administration has asserted that no-one in government had envisioned a suicide hijacking before it happened.

White House press secretary Ari Fleischer said the administration was aware of the report, which was prepared by the Library of Congress for the National Intelligence Council, which advises the president and US intelligence on emerging threats.

Our nation is not well served when the charge of partisan politics is levelled at those who simply seek information that the American people need and deserve to know

Democrat Richard Gephard

He said the document did not contain direct intelligence pointing towards a specific plot but rather included assessments about how terrorists might strike.

"What it shows is that this information that was out there did not raise enough alarm with anybody," Mr Fleischer said.

He indicated that he found the criticism of the president unacceptable.

"I think that any time anybody suggests or implies to the American people that this president had specific information that could have prevented the attacks on our country on 11 September, that crosses the lines," he said.

But the Democrat House minority leader, Richard Gephardt called for a congressional inquiry into the affair.

"Our nation is not well served when the charge of partisan politics is levelled at those who simply seek information that the American people need and deserve to know," he said.

About 3,000 people died in the 11 September attacks

The White House had earlier revealed that a presidential order to topple the al-Qaeda network was prepared just before 11 September. But the proposals had not reached Mr Bush at the time of the attacks.

Information also emerged about a memo from the FBI's Phoenix office last July warning headquarters that a large number of Arabs were training at a US flight school.

"This memo was very consequential and should have been analysed at the highest levels of the intelligence community," said Democratic Senator Dianne Feinstein.

"Sadly it was not."