There is no evidence deposed President Saddam Hussein had ties with Al-Qaeda, according to a Senate report on prewar intelligence that Democrats say undercuts President George W Bush's justification for invading Iraq.
Bush administration officials have insisted on a link between the Iraqi regime and terror leader Abu Musab al-Zarqawi. Intelligence agencies, however, concluded there was none.
Republicans countered that there was little new in the report and Democrats were trying to score election-year points with it.
The declassified document released on Thursday by the 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.
It concludes that postwar findings do not support a 2002 intelligence community report that Iraq was reconstituting its nuclear programme, possessed biological weapons or ever developed mobile facilities for producing biological warfare agents.
The 400-page report comes at a time when 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 in November.
It discloses for the first time an October 2005 CIA assessment that prior to the war Saddam's government "did not have a relationship, harbour, or turn a blind eye toward Zarqawi and his associates."
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.