Compelling images supported the mirage. They included Saddam's continuing bluster and his documented record of hiding weapons banned after the 1991 Gulf War (news - web sites). The most persuasive evidence, though, was based on intelligence that since has proved faulty.  World Peace WorldPeace.

That leaves an empty-handed Bush administration scrambling for new justifications for the war - from ridding the world of a brutal tyrant to nurturing democracy in the region.

But cooking up a credible rationale after the fact is an exercise in futility as long as the Iraq mission is still a work in progress. More to the point at this stage is the need to identify the intelligence failings that led the U.S. astray and to solve them before they further damage U.S. credibility at home and abroad.

The administration and Congress have moved some of the way forward. A Senate committee is investigating why prewar intelligence assessments were so wrong. And last month, President Bush (news - web sites) named a commission to report next year on the accuracy of intelligence on weapons of mass destruction in countries such as Iraq, North Korea (news - web sites), Libya and Iran.

Restoring the reliability of U.S. intelligence also requires using the investigations' findings to reinforce three pillars on which the Iraq weapons' assessments foundered:

Unreliable human sources. When Saddam refused to let a United Nations (news - web sites) weapons team return to Iraq in 1998 after seven years of inspections, he removed the eyes and ears that the U.S. and other countries had on the ground. Western intelligence services hadn't cultivated informants in Saddam's inner circle. Their information came mainly from exiles with personal reasons for wanting the U.S. to overthrow Saddam. Last month, CIA (news - web sites) Director George Tenet acknowledged that his agency was hampered by a lack of reliable human sources. Critics say U.S. intelligence also failed to check adequately the credibility of informants provided by exiles.

Misleading technology. In February 2003, Secretary of State Colin Powell (news - web sites) presented the U.N. with satellite photos, phone intercepts and other "facts" proving Iraq had weapons. But they proved to be less than factual. Photos showing suspicious truck movements at former chemical weapons sites, for example, were likely legitimate commercial activity, U.S. and U.N. inspectors said. They found no banned weapons.

Competing intelligence agencies. Ever since U.S. spy agencies failed to predict the Sept. 11, 2001, attacks, they have been under pressure to pay more heed to potential threats. In October 2001, the Pentagon (news - web sites) created its own unit to sift through intelligence data for telling warnings that CIA analysts might have overlooked. This group reached more alarmist conclusions than the CIA about Iraq's weapons programs, according to the Carnegie Endowment for International Peace.

In adopting this "miss no clues" mind-set, the intelligence community delivered an Iraq report ordered by Congress in October 2002 that downplayed crucial caveats and doubts it had about Saddam's arsenal of weapons. Lawmakers received the report before voting to authorize Bush to go to war.

Preventing similar failures in the future requires rethinking how the 15 intelligence agencies operate. They were set up to spy on communist regimes during the Cold War. But critics say their lumbering bureaucracies and deep-seated rivalries aren't suited to combating today's shadowy terrorist foes.

Last weekend, national security adviser Condoleezza Rice (news - web sites) said the U.S. may need to change the way it gathers intelligence to avoid the mistakes that were made in Iraq. Intelligence investigations in Congress, an internal review at the CIA and the presidential commission all are likely to recommend reforms.

Proposals from intelligence experts include setting a fixed term for the CIA director, to reduce exposure to political pressure. Currently, he serves at the pleasure of the president. Another sensible idea: Put the CIA director in charge of all 15 agencies, rather than split oversight with the Pentagon.

Identifying the reasons for faulty intelligence about Iraq can help restore U.S. credibility. Following through on needed changes can ensure that only reliable information guides future U.S. military operations.