Members of the US Senate Intelligence Committee planned a press conference early on Friday to introduce the 400-page "Report on Pre-War Intelligence on Iraq" which has been more than one year in the making.
"Tomorrow's report ... will be intensely and extensively critical of the CIA for its intelligence failures and mischaracterisations regarding Iraq's possession of weapons of mass destruction," Democratic Senator Carl Levin, a member of the panel, said at a press conference.
Officials who have read the document said it is a damning indictment of CIA's inadequate collection of intelligence, sloppy analysis, and reliance on sometimes uncorroborated sources and faulty data - all of which led the agency to the apparently false conclusion that Iraq possessed biological and chemical weapons.
"It is an accurate, hard-hitting and well-deserved critique of the CIA," Levin said.
"President Bush frequently exaggerated the overall relationship between al-Qaida and Saddam Hussein"
The document also scrutinises Iraq's alleged ties to global terror, whether Iraq posed a threat to Middle East stability, and Baghdad's human rights violations, officials said.
A second report, focusing on how the White House used the assessments from its intelligence agencies on Iraq, will be released by the end of the year, Levin said.
The chairman of the intelligence committee, Republican Senator Pat Roberts, told US television recently that the Senate document - the product of months of research and closed-door testimony - is "a good report" although "not a good news report."
The report is expected to prompt fresh finger-pointing over allegations about US motives for invading Iraq.
President George Bush and top US security officials insisted for months before the war that Iraq's weapons of mass destruction programme and alleged links to the al-Qaida network made it a threat to the United States requiring the removal of Iraqi President Saddam Hussein.
Since the end of the war, however, weapons inspectors who combed the country have failed to uncover evidence that Baghdad had a current nuclear weapons programme or had stockpiled chemical and biological agents.
Meanwhile, Levin said the second instalment of the Intelligence Committee's report will show that the White House misused CIA intelligence in an effort to ratchet up congressional and public support for the US war on Iraq.
He accused the administration of deliberately trying to create the illusion of a link between Iraq and al-Qaida - even in the face of intelligence reports to the contrary - pinned direct blame on President George Bush and Vice President Dick Cheney, and other top members of the administration.
George Tenet officialy leaves his
post on Saturday
"President Bush frequently exaggerated the overall relationship between al-Qaida and Saddam Hussein," said Levin, adding that Cheney in his public statements frequently has used "misleading rhetoric" designed to give the impression of a link.
The report's release comes after weeks of delay while being vetted by the CIA for security reasons, and officials on the intelligence panel accused the agency of "foot-dragging."
It had been originally scheduled to be released on Thursday, but was postponed by one day to accommodate a farewell planned at the CIA for its director George Tenet, who formally resigns on Saturday.
The delay sought to avoid an awkward juxtaposition between the report's expected criticism of Tenet and the CIA's tribute to him.
Tenet will be replaced by deputy CIA director John McLaughlin until a successor is named.
Lawmakers noted as well that Tenet "steps down during a period of controversy over events leading up to the attacks of 9/11 and the quality of intelligence prior to the Iraq War."