In a scathing report, the Senate Select Committee on Intelligence blamed the CIA for falling prey to "false group think," and faulted outgoing director George Tenet.
The report was approved unanimously by the committee despite months of partisan bickering over whether to investigate how President Bush and other officials used the intelligence in making their case for war.
"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 biological and chemical weapons and, if left unchecked, would probably have a nuclear weapon within this decade," intelligence committee chairman Pat Roberts, -R-Kan., said. "Today we know these assessments were wrong."
Roberts said the intelligence assessments had been "unreasonable and largely unsupported by the available intelligence." He called the committee's investigation of the prewar intelligence unprecedented.
"This has not been a pleasant task but it is based on fact," Roberts said.
The false group think "caused the community to interpret ambiguous evidence" such as Iraq's obtaining materials with possible dual use for civilian as well as military purposes, "as conclusive evidence," Roberts said.
The problems "extended to our allies and to the United Nations and other nations as well, all of whom believed that Saddam Hussein had active WMD programs."
"This was a global intelligence failure," Roberts said. Inside the U.S. spy agencies, he said, the intelligence flaws were the result of "broken corporate culture and poor management and cannot be solved by simply adding funding and personnel."
Roberts said that after the U.N. inspectors left Iraqi in 1998, the CIA had no human intelligence sources focusing on weapons of mass destruction in Iraq. The CIA also "sequestered" information from some analysts.
Similar problems affected efforts to understand possible links between Saddam's regime and terrorists. However, Roberts said, the committee found the CIA's reporting on Saddam and terrorism reasonable. Those reports included a more honest acknowledgment of doubts about the intelligence.
"In the end what the president and the Congress used to send the country to war was information that was provided by the intelligence community and the information was flawed," Roberts said.
The ranking Democrat on the panel, Sen. Jay Rockefeller of West Virginia, said, "There is simply no question that mistakes leading up to the war in Iraq rank among the most devastating losses and intelligence failures in the history of the nation."
"The administration at all levels and (Congress) used bad information to bolster its case for going to war," Rockefeller said. "We would not have authorized that war if we knew what we know now."
Rockefeller said the committee report failed to pay adequate attention to how intelligence was used by the Bush administration. Democrats on the panel are pressing for a second phase of the investigation to cover the use of intelligence.
Highlighting one area of disagreement within the committee, Roberts said CIA analysts complained of no political pressure. But Rockefellers said the CIA was producing reports when Bush administration officials had already announced their conclusion that Saddam possessed weapons of mass destruction.
The report repeatedly blasts departing Tenet, accusing him of skewing advice to top policy-makers with the CIA's view and elbowing out dissenting views from other intelligence agencies overseen by the State or Defense Departments.
It faulted Tenet for not personally reviewing Mr. Bush's 2003 State of the Union address, which contained since-discredited references to Iraq's attempts to purchase uranium in Africa.
Tenet has resigned and leaves office this week.
Intelligence analysts worked from the assumption that Iraq had chemical and biological weapons and was seeking to make more, as well as trying to revive a nuclear weapons program. Instead, investigations after the Iraq invasion have shown that Iraqi dictator Saddam Hussein had no nuclear weapons program and no biological weapons, and only small amounts of chemical weapons have been found.
Analysts ignored or discounted conflicting information because of their assumptions that Iraq had weapons of mass destruction, the report says.
Such assumptions also led analysts to inflate snippets of questionable information into broad declarations that Iraq had chemical and biological weapons, the report says.
For example, speculation that the presence of one specialized truck could mean an effort to transfer chemical weapons was puffed up into a conclusion that Iraq was actively making chemical weapons, the report says.
Analysts also concluded that Iraq had a mobile biological weapons program based mainly on the since-discredited claims of one Iraqi defector code-named "Curve Ball," it says. American agents did not have direct access to Curve Ball or his debriefers, but the source's information was expanded into the conclusion that Iraq had an advanced and active biological weapons program, the report says.
The report comes as Mr. Bush is deciding when to nominate a permanent replacement for Tenet, whose . Tenet's deputy, John McLaughlin, will then take over.
Tenet has said his agency's analysts " never said there was an imminent threat." But in Bob Woodward's book "Plan of Attack," Tenet is quoted as telling Mr. Bush that the evidence of Iraqi weapons work was "a slam dunk."
However, there were differences between how classified CIA reports and public presentations described Iraq's capabilities.
For example, the crucial National Intelligence Estimate on Iraq, drafted in October 2002, reveal doubts by some intelligence agencies about the extent of its nuclear program, the purpose of work its on unmanned aircraft, its doctrine for using WMD and the circumstances under which Saddam Hussein might partner with al Qaeda.
Administration officials rarely, if ever, hinted at those doubts.
The Senate report is among a litany of investigations under way into the intelligence community's recent performance. Mr. Bush named two commissions to investigate the and U.S. intelligence capabilities regarding .