In a hard-hitting report released today, the U.S. Senate's Select Committee on Intelligence said the CIA and other agencies used unfounded "group think" assumptions to assess the existence of weapons of mass destruction in Iraq before last year's U.S. invasion and reached conclusions that were often either "overstated" or "not supported by the underlying intelligence."

"A series of failures, particularly in analytic trade craft, led to the mischaracterization of intelligence" about Iraqi weapons programs, the committee concluded, according to the report.

The 511-page report, the product of the committee's year-long investigation of pre-war intelligence on Iraq, also pointed to severe management problems at the CIA. The agency's director, George J. Tenet, announced his resignation last month for personal reasons and leaves office Sunday.

In accusing the CIA and its top leaders of engaging in a "group think dynamic," the committee said analysts and senior policymakers never questioned their long-held assumption that Iraq possessed weapons of mass destruction. In addition, the committee reported, the CIA had no undercover agents in Iraq since 1998 to help gather reliable information and failed to tell policymakers of "the uncertainties of both the reliability of some key sources and of intelligence judgments."

Reacting to the report, CIA Deputy Director John E. McLaughlin told reporters this afternoon, "My first message to you is a very simple one: We get it."

In a briefing at CIA headquarters in Northern Virginia, he said, "Although we think the judgments were not unreasonable when they were made nearly two years ago, we understand with all we have learned since then that we could have done better."

Asked if anyone at the agency would be fired over the intelligence failure, McLaughlin said the CIA must not be "risk averse." He added, "I can think of nothing that would be more effective in generating aversion to risk than to hold an individual personally accountable for a mistake that might have been made by hundreds of people around the world. . . ."

President Bush called the report "useful" and said he looked forward to working with Congress on reforming the intelligence community.

"The idea that the Senate has taken a hard look to find out where the intelligence-gathering services went short is good and positive," Bush said during a political campaign stop in Kutztown, Pa. "We need to know. I want to know. I want to know how to make the agencies better, to make sure that we're better able to gather the information necessary to protect the American people."

Bush said that among the needed reforms were measures to "bolster human intelligence," make better use of technology and improve coordination among intelligence-gathering agencies.

While the committee's nine Republicans and eight Democrats voted unanimously to release the report, they expressed some differences about whether the Bush administration exerted undue political pressure on the intelligence community to provide assessments that supported a decision to go to war in Iraq. And Democrats lamented that a second phase of the committee's investigation -- into how the administration used the intelligence it received -- will not be completed until well after the November elections.

"Now it's important that we stop pointing fingers and we get to the bottom of the fact, to make sure we don't do this again," said Dan Bartlett, the White House communications director, in an interview on CNN after the report was released.

In a joint news conference to present the report, the committee's Republican chairman and Democratic vice chairman agreed that the CIA and other U.S. intelligence agencies had suffered a massive intelligence failure in assessing chemical, biological and nuclear weapons programs in Iraq before the March 2003 U.S. invasion.

"The debate over many aspects of the U.S. liberation of Iraq will likely continue for decades," said Sen. Pat Roberts (R-Kan.), the chairman of the committee. "But one fact is now clear: before the war, the U.S. intelligence community told the president, as well as the Congress and the public, that Saddam Hussein had stockpiles of chemical and biological weapons and, if left unchecked, would probably have a nuclear weapon during this decade. Today we know these assessments were wrong."

Moreover, he said, the report shows that "they were also unreasonable and largely unsupported by the available intelligence."

Asked if he believed Congress would have authorized the use of force against Iraq had it known the weakness of the intelligence on Iraq's weapons of mass destruction, Roberts said, "I do not know." He said he would have voted for the war in Iraq on humanitarian grounds, but that it would have been a different kind of war. He said it would have been more similar to the U.S. interventions in Kosovo and Bosnia in the 1990s -- an apparent reference to the fact that U.S. ground troops were not deployed in either of those conflicts.

"I think it would have been argued differently," he said. "I think perhaps the battle plan would have been different."

Sen. John D. "Jay" Rockefeller IV (D-W.Va), the committee's vice chairman, said categorically that Congress would have rejected going to war in Iraq if not for the faulty intelligence.

Roberts told the news conference that, among other findings, "the committee concluded that the intelligence community was suffering from . . . a collective group-think." He said this caused the intelligence community "to interpret ambiguous elements . . . as conclusive evidence of the existence of WMD [weapons of mass destruction] programs." But the group-think also extended to U.S. allies, the United Nations and other countries, he said.

"This was a global intelligence failure," Roberts said.

He said the committee found the CIA riddled by "a broken corporate culture and poor management," but he insisted that political pressure from the Bush administration did not produce the faulty assessments.

"In the end, what the president and Congress used to send the country to war was provided by the intelligence community, and that information was flawed," Roberts said. "This report cries out for reform."

Rockefeller called the assessments of Iraq before the 2003 war "one of the most devastating intelligence failures in the history of the nation."

He said, "We in Congress would not have authorized that war, with 75 votes, if we knew what we know now." While the government "didn't connect the dots" in analyzing clues before the Sept. 11, 2001, terrorist attacks, he said, "in Iraq we were even more culpable, because the dots themselves never existed."

The intelligence failures detailed in the report will affect U.S. national security for generations to come, Rockefeller said.

"Our credibility is diminished," he said. "Our standing in the world has never been lower. We have fostered a deep hatred of Americans in the Muslim world, and that will grow. As a direct consequence, our nation is more vulnerable today than ever before."

In the news conference, Roberts and Rockefeller displayed the partisan differences that have surfaced over the issue of political pressure on the CIA, a subject that Rockefeller said had produced "major disagreements" on the committee. He said he felt "that the definition of pressure was very narrowly drawn in the final report" and that statements by Tenet and other CIA officials indicated that such pressure existed.

Roberts said there was pressure from policy-makers to be "forward-leaning" and come up with information. But he said, "I do not think there is any evidence of undue pressure on any analysts" with regard to assessments of Iraqi weapons of mass destruction.

He said he expects President Bush to support the committee's calls for reform of the intelligence community.

"What he said [about Iraq's banned weapons] was what he got from the intelligence community, and what he got was wrong," Roberts said. "So he more than anybody will want to work with us" on reform efforts.

The thick report, which was heavily redacted by the CIA, represents the first phase of a two-part review of intelligence on Iraq. Left for the second phase -- in a second report likely to come out sometime next year -- is the issue of the Bush administration's use of the intelligence that was provided to it.

Before the report was issued, Sen. Carl M. Levin (D-Mich.), a senior Democrat on the committee, said the document highlights "failures of leadership in the CIA." Despite the Bush administration's preparations to attack Iraq last year, Levin told NBC's "Today Show" this morning, "They just weren't ready at the CIA."

He added: "But I think it's also clear that they were shaping intelligence in order to meet the policy needs of the administration. There can't be much doubt about that as an explanation."

Interviewed on the same program, Sen. Olympia J. Snowe (R-Maine) said that view "isn't fair" and does not represent the committee's unanimous conclusion.

She said, "What happened here was a systemic failure throughout the intelligence community. . . . There was no human intelligence operations. They didn't place a priority on it. So there was failure across the board within the community.

"No analyst is going to say they changed their view as a result of specific pressure," Levin countered. "No analyst is going to admit that. But there is no doubt and this report reflects the fact that there was tremendous pressure inside the agency. As a matter of fact, Tenet himself said, and this report reflects that, that he was told by analysts that they were under tremendous pressure. And what Tenet said is, well, in that case, just try to ignore that pressure. But the pressure was clearly there."

Yesterday, Levin said in a press conference that the report "does not purport to address the central issue of the administration's exaggerations of the intelligence that was provided to them by the CIA. That issue is left for the second phase of the Intelligence Committee's investigation."

Levin said that "many, many questions that we have asked the CIA remain unanswered. . . ." But one question that was answered only Wednesday, he said, "demonstrates that it was the administration, not the CIA, that exaggerated the relations between Saddam Hussein and al Qaeda."

He said the CIA found that, contrary to assertions by Vice President Cheney and other officials, there was no credible information that a purported meeting in Prague in April 2001 between an Iraqi intelligence agent and Mohamed Atta, one of the Sept. 11 hijackers, actually occurred.