The usual channels for intelligence assessment were sidestepped too, contributing to incorrect prewar assertions that Saddam Hussein possessed weapons of mass destruction.

The Bush administration based a crucial prewar assertion about ties between Iraq and Al Qaeda on detailed statements made by a prisoner while in Egyptian custody who later said he had fabricated them to escape harsh treatment, according to current and former government officials.

General Clapper's comments came as the Central Intelligence Agency prepared to defend its prewar assertions that Iraq had chemical and biological weapons and that it sought to reconstitute its nuclear program.

The assertion that Iraq provided refuge to Mr. Zarqawi was the primary basis for the administration's prewar assertions connecting Iraq to Al Qaeda.

But the Intelligence Committee's report again focused attention on Mr. Bush's prewar assertions that Iraq had weapons that were banned and was therefore a threat to use them itself or pass them to terrorists.

The failure so far of American investigators in Iraq to uncover evidence of illicit weapons has called into question the Bush administration's prewar assertions that Iraq possessed chemical and biological weapons and was seeking to reconstitute its nuclear program.

The fact that no chemical or biological weapons have been found in Iraq, despite prewar assertions by American intelligence agencies that Iraq possessed such devices, is only the most recent sign of those flaws, she said.

In a report last summer, the Senate committee was scathing in its conclusions about American intelligence on Iraq, saying that prewar assertions that Baghdad possessed chemical and biological weapons had not been supported by information available at the time.

They also show the enormous distance between the Bush administration's own prewar assertions, based on reports by American intelligence agencies, and what a 15-month inquiry by American investigators found since the war.

In 2004, the independent Sept. 11 commission said it had seen "no evidence" that the contacts "ever developed into a collaborative operational relationship," challenging the administration's prewar assertions.