The declassified document being released Friday by the Senate Intelligence Committee also explores the role that inaccurate information supplied by the anti-Saddam exile group the Iraqi National Congress had in the march to war.
The report comes at a time when Mr. Bush is emphasizing the need to prevail in Iraq to win the war on terrorism while Democrats are seeking to make that policy an issue in the midterm elections.
It discloses for the first time an October 2005 CIA assessment that prior to the war Saddam's government "did not have a relationship, harbor, or turn a blind eye toward Zarqawi and his associates," according to excerpts of the 400-page report provided by Democrats.
Mr. Bush and other administration officials have said that the presence of Zarqawi in Iraq before the war was evidence of a connection between Saddam's government and al Qaeda. Zarqawi was killed by a U.S. airstrike in June this year.
White House press secretary Tony Snow played down the report as "nothing new."
"In 2002 and 2003, members of both parties got a good look at the intelligence we had and they came to the very same conclusions about what was going on," Snow said. That was "one of the reasons you had overwhelming majorities in the United States Senate and the House for taking action against Saddam Hussein," he said.
Read the Senate committee report on information provided by the Iraqi National Congress.
Read the Senate committee report on Iraq's alleged terror links.
Warning: These are large files.
Sen. Carl Levin, D-Mich., a member of the committee, said the long-awaited report was "a devastating indictment of the Bush-Cheney administration's unrelenting, misleading and deceptive attempts" to link Saddam to al Qaeda.
The administration, said Sen. John D. Rockefeller, D-W.Va., top Democrat on the committee, "exploited the deep sense of insecurity among Americans in the immediate aftermath of the Sept. 11 attacks, leading a large majority of Americans to believe — contrary to the intelligence assessments at the time — that Iraq had a role in the 9/11 attacks."
The chairman of the committee, Sen. Pat Roberts, R-Kan., said it has long been known that prewar assessments of Iraq "were a tragic intelligence failure."
But he said the Democratic interpretations expressed in the report "are little more than a vehicle to advance election-year political charges." He said Democrats "continue to use the committee to try and rewrite history, insisting that they were deliberately duped into supporting the overthrow of Saddam Hussein's regime."
The panel report is Phase II of an analysis of prewar intelligence on Iraq. The first phase, issued in July 2004, focused on the CIA's failings in its estimates of Iraq's weapons program.
The second phase has been delayed as Republicans and Democrats fought over what information should be declassified and how much the committee should delve into the question of how policymakers may have manipulated intelligence to make the case for war.
The committee is still considering three other issues as part of its Phase II analysis, including statements of policymakers in the run up to the war.
Republican members of the intelligence committee would not comment on the report Thursday, but Democrats, who have been pushing for its release, said it backed up their argument that Mr. Bush's case for war in Iraq was misleading.
Democrats have argued that Chalabi, in his campaign to topple Saddam, fed U.S. intelligence agencies information that exaggerated the threat posed by Iraq's WMD capabilities. Republicans have countered that Chalabi's influence was limited.