WASHINGTON — The CIA last fall repudiated the claim that there were prewar ties between Saddam Hussein's government and an operative of al-Qaida, Abu Musab al-Zarqawi, according to a report issued on Friday by the Senate Intelligence Committee.

The disclosure undercuts continuing assertions by the Bush administration that such ties existed, and that they provided evidence of links between Iraq and al-Qaida. The Republican-controlled committee also sharply criticized the administration for its reliance on the Iraqi National Congress during the prelude to the war in Iraq.

The findings, in two new reports, are part of an ongoing inquiry by the committee into prewar intelligence about Iraq. The conclusions went beyond its earlier findings, issued in the summer of 2004, by including criticism not just of American intelligence agencies but also of the administration.

Several Republicans strongly dissented from the conclusions in the report about the Iraqi National Congress, saying they overstated the role that the exile group played in the prewar intelligence assessments about Iraq. But the committee overwhelmingly approved the other report, with only one Republican senator voting against it.

The reports did not address the politically divisive question of whether the Bush administration had exaggerated or misused intelligence as part of its effort to win support for the invasion of Iraq. But one report did contradict the administration's assertions, made before the war and since, that ties between al- Zarqawi and Saddam's government provided evidence of a close relationship between Iraq and al-Qaida.

As recently as Aug. 21, President Bush said at a news conference that Saddam "had relations with Zarqawi." But a CIA report completed in October 2005 concluded instead that Saddam's government "did not have a relationship, harbor or even turn a blind eye toward Zarqawi and his associates," according to the new Senate findings.

The CIA report also directly contradicted claims made in February 2003 by Secretary of State Colin L. Powell, who mentioned al- Zarqawi by name no fewer than 20 times during a speech to the United Nations Security Council that made the administration's case to go to war. In that speech, Powell said that Iraq "today harbors a deadly terrorist network" headed by al-Zarqawi, and dismissed as "not credible" assertions by the Iraqi government that it had no knowledge of al-Zarqawi's whereabouts.

In fact, the Senate investigation concluded that Saddam regarded al-Qaida as a threat rather than a potential ally, and that the Iraqi intelligence service "actively attempted to locate and capture al-Zarqawi without success."

The 356-page report by the committee specifically criticized a decision by the National Security Council in 2002 to maintain a close relationship with the Iraqi National Congress, headed by the exile leader Ahmad Chalabi, even after the CIA and the Defense Intelligence Agency had warned that "the INC was penetrated by hostile intelligence services," notably Iran.

The report concluded that the INC had provided a large volume of flawed intelligence to the United States about Iraq, and concluded that the group "attempted to influence United States policy on Iraq by providing false information through defectors directed at convincing the United States that Iraq possessed weapons of mass destruction and had links to terrorists."

The findings and their release came at an inopportune time for the Bush administration, which has spent the week trying to turn voters' attention away from the missteps on Iraq and toward the more comfortable political territory of the continued terrorist threat to the United States.

On Friday, the White House spokesman, Tony Snow, downplayed the reports, saying that they contained "nothing new" and were "re-litigating things that happened three years ago."

"The important thing to do is to figure out what you're doing tomorrow, and the day after, and the month after, and the year after to make sure that this war on terror is won," Snow said.

The two reports released Friday are expected to be the least controversial aspects of what remains of the Senate committee's investigation, which will eventually address the question of whether the Bush administration's assertions about Iraq accurately reflected the available intelligence.

But their completion had been delayed for months, and their release in the midst of a White House campaign that emphasized terrorism appeared to have occurred by coincidence.

The reports were actually approved by the committee in August, but went through a month-long declassification process. It was Sen. Pat Roberts of Kansas, the committee's Republican chairman, who set early September as the release date.

The committee's initial report in 2004, which lambasted intelligence agencies for vastly overestimating the state of Iraq's nuclear, biological and chemical weapons programs, was issued with unanimous approval. But the reports released on Friday provided evidence of how much the relationship between Republicans and Democrats on the committee has degenerated over the past two years.

A set of conclusions that included criticism of the administration's ties with the Iraqi National Congress was opposed by several Republicans on the panel, including Roberts, but was approved with the support of two Republicans, Chuck Hagel of Nebraska and Olympia Snowe of Maine, along with all seven Democrats. Roberts even took the unusual step of disavowing the conclusions about the role played by the INC, saying that they were "misleading and are not supported by the facts."

The report about the INC's role concluded that faulty intelligence from the group made its way into several prewar intelligence reports, including the October 2002 National Intelligence Estimate that directly preceded the Senate vote on the Iraq war. It says that sources introduced to American intelligence by the group directly influenced two key judgments of that document: that Saddam possessed mobile biological weapons laboratories and that he was trying to reconstitute his nuclear program.

The report said there was insufficient evidence to determine whether one of the most notorious of the intelligence sources used by the United States before the Iraq war was tied to the Iraqi National Congress. The source, an Iraqi national code-named Curveball, was a critical source for the American view that Saddam had a mobile biological weapons program, but the information that he provided was later entirely discredited.

The report said other mistaken information about Iraq's biological program had been provided by a source linked to the Iraqi National Congress, and it said the intelligence agencies' use of the information had "constituted a serious error."

The dissenting opinion, signed by Roberts and four other Republican members of the committee, minimizes the role played by Chalabi's group. "Information from the INC and INC-affiliated defectors was not widely used in Intelligence Community products and played little role in the Intelligence Community's judgments about Iraq's WMD programs," the Republicans said.

Francis Brooke, an INC spokesman, called the report "tendentious, partisan and misleading," and agreed with the Republican dissent that the INC did not play a central role as the Bush administration built the case for war.

At the same time, Brooke said his organization was surprised at how little the American government actually knew about Saddam's regime before the Iraq war, which may have forced the American officials to rely more heavily on the INC

"We did not realize the paucity of human intelligence that the administration had on Iraq," Brooke said.