WASHINGTON (CNN) -- In a highly critical report issued Friday, the U.S. Senate Intelligence Committee found that the CIA's prewar estimates of Iraq's weapons of mass destruction were overstated and unsupported by intelligence.
Committee Chairman Pat Roberts, R-Kansas, told reporters that intelligence used to support the invasion of Iraq was based on assessments that were "unreasonable and largely unsupported by the available intelligence."
The committee's conclusions are contained in a 511-page report released Friday.
"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," Roberts said.
"Today we know these assessments were wrong."
Sen. Jay Rockefeller, the leading Democrat on the 18-member panel, said that "bad information" was used to bolster the case for war.
"We in Congress would not have authorized that war with 75 votes if we knew what we know now," the West Virginia Democrat said.
"Leading up to September 11, our government didn't connect the dots. In Iraq, we are even more culpable because the dots themselves never existed."
Roberts listed several points emphasized in the October 2002 National Intelligence Estimate that were "overstated or "not supported by the raw intelligence reporting."
Among these were that Iraq was reconstituting its nuclear program, had chemical and biological weapons, and was developing an unmanned aerial vehicle, probably intended to deliver biological warfare agents.
He also said the intelligence community failed to "accurately or adequately explain the uncertainties behind the judgments in the October 2002 National Intelligence Estimate to policymakers."
Rockefeller said that the "intelligence failures" will haunt America's national security "for generations to come."
"Our credibility is diminished. Our standing in the world has never been lower," he said. "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."
The top-ranking members of the Senate committee offered different interpretations on political pressures on the intelligence community.
"The committee found no evidence that the intelligence community's mischaracterization or exaggeration of intelligence on Iraq's weapons of mass destruction capabilities was the result of politics or pressure," Roberts said.
But although he approved the report, Rockefeller said it fails to explain fully the pressures on the intelligence community "when the most senior officials in the Bush administration had already forcefully and repeatedly stated their conclusions publicly."
"It was clear to all of us in this room who were watching that -- and to many others -- that they had made up their mind that they were going to go to war," he said.
Critics of the war had expressed concerned about visits to the CIA by Vice President Dick Cheney and other officials, but the report said it found no evidence that policymakers asked inappropriate questions of analysts or tried to pressure them into changing their views.
Some GOP lawmakers on the panel successfully blocked Democratic efforts to finish the second part of the report -- how the Bush administration used the information from the intelligence community -- until after the November elections.
Rep. Jane Harman, D-California, said she hoped a similar investigation from the House of Representatives would address some of those issues, adding she was frustrated in her attempts to get the investigation off the ground.
"There has not been the cooperation that there apparently has been on the Senate side," said Harman, the top Democrat on the House Intelligence Committee.
She said she had written to committee Chairman Porter Goss, R-Florida, four times. "And just today we were able to sit down together," Harman said.
Goss, a former CIA agent, has been mentioned as a possible replacement for outgoing CIA Director George Tenet, who was blasted in the Senate report. Tenet has resigned and leaves office Sunday.
"I would hope we could address [the issues] factually and on a bipartisan basis, but at the moment I don't have a lot of confidence in it," Harman said.
Rockefeller said the administration's position was that Iraq stockpiled weapons and actively pursued a nuclear weapons program and that it "might use its alliances with terrorist organizations, including al Qaeda, to use these weapons to strike at the United States."
Rockefeller said that "no evidence existed of Iraq's complicity or assistance in al Qaeda's terrorist attacks, including 9/11."
The report said that intelligence analysts were "accurate and not affected by a lack of relevant source or operational detail" in making a connection between Iraq and terrorism -- although it did say that contacts between al Qaeda and Iraq in the 1990s "did not add up to an established formal relationship."
Roberts: Case for war based on 'flawed' information
Roberts said President Bush and Congress sent the country to war based on "flawed" information provided by the intelligence community.
He said the panel concluded that the intelligence community suffered "from what we call a collective group think, which led analysts and collectors and managers to presume that Iraq had active and growing WMD programs."
Roberts said this "group think caused the community to interpret ambiguous evidence, such as the procurement of dual-use technology, as conclusive evidence of the existence of WMD programs."
The report criticized the CIA and Defense Intelligence Agency's Defense Human Intelligence Service for their handling of an informer code-named "Curveball," noting that the latter "demonstrated serious lapses in handling such an important source."
Over and over, the report noted, analysts had exaggerated what they knew and left out, glossed over or simply dismissed dissenting views.
The report said that the intelligence community eliminated caveats about assessments when it compiled a document hurriedly released to the public in October 2002, thus misrepresenting "their judgments to the public which did not have access to the classified National Intelligence Estimate containing the more carefully worded assessments."
The National Intelligence Estimate was used to persuade Congress to authorize war, but administration officials for weeks already had been putting out the kind of information found in it.
Regarding Secretary of State Colin Powell's February 2003 speech to the United Nations -- in which he presented the U.S. case for war -- the report said that much of the information from the CIA "was overstated, misleading or incorrect."
Roberts said the most troubling finding was the lack of human intelligence in Iraq.
"Most alarmingly, after 1998 and the exit of the U.N. inspectors, the CIA had no human intelligence sources inside Iraq who were collecting against the WMD target," Roberts said.
He said most of the problems come from a "broken corporate culture and poor management and cannot be solved by simply adding funding and also personnel."
Roberts also called intelligence failures before the war "global" and not confined to the United States.