The eight-page memo, written in advance of a July 23, 2002, Downing Street meeting on Iraq, provides new insights into how senior British officials saw a Bush administration decision to go to war as inevitable, and realized more clearly than their American counterparts the potential for the post-invasion instability that continues to plague Iraq.

In its introduction, the memo "Iraq: Conditions for Military Action" notes that U.S. "military planning for action against Iraq is proceeding apace," but adds that "little thought" has been given to, among other things, "the aftermath and how to shape it."

The July 21 memo was produced by Blair's staff in preparation for a meeting with his national security team two days later that has become controversial on both sides of the Atlantic since last month's disclosure of official notes summarizing the session.

In those meeting minutes -- which have come to be known as the Downing Street Memo -- British officials who had just returned from Washington said Bush and his aides believed war was inevitable and were determined to use intelligence about Saddam Hussein's weapons of mass destruction and his relations with terrorists to justify invasion of Iraq.

The "intelligence and facts were being fixed around the policy," said the memo -- an assertion attributed to the then-chief of British intelligence, and denied by U.S. officials and by Blair at a news conference with Bush last week in Washington. Democrats in Congress led by Rep. John Conyers Jr. (Mich.), however, have scheduled an unofficial hearing on the matter for Thursday.

Now, disclosure of the memo written in advance of that meeting -- and other British documents recently made public -- show that Blair's aides were not just concerned about Washington's justifications for invasion but also believed the Bush team lacked understanding of what could happen in the aftermath.

In a section titled "Benefits/Risks," the July 21 memo states, "Even with a legal base and a viable military plan, we would still need to ensure that the benefits of action outweigh the risks."

Saying that "we need to be sure that the outcome of the military action would match our objective," the memo's authors point out, "A post-war occupation of Iraq could lead to a protracted and costly nation-building exercise." The authors add, "As already made clear, the U.S. military plans are virtually silent on this point. Washington could look to us to share a disproportionate share of the burden."

That memo and other internal British government documents were originally obtained by Michael Smith, who writes for the London Sunday Times. Excerpts were made available to The Washington Post, and the material was confirmed as authentic by British sources who sought anonymity because they are not authorized to discuss the matter.

The Bush administration's failure to plan adequately for the postwar period has been well documented. The Pentagon, for example, ignored extensive State Department studies of how to achieve stability after an invasion, administer a postwar government and rebuild the country. And administration officials have acknowledged the mistake of dismantling the Iraqi army and canceling pensions to its veteran officers -- which many say hindered security, enhanced anti-U.S. feeling and aided what would later become a violent insurgency.

Testimony by then-Deputy Secretary of Defense Paul D. Wolfowitz, one of the chief architects of Iraq policy, before a House subcommittee on Feb. 28, 2003, just weeks before the invasion, illustrated the optimistic view the administration had of postwar Iraq. He said containment of Hussein the previous 12 years had cost "slightly over $30 billion," adding, "I can't imagine anyone here wanting to spend another $30 billion to be there for another 12 years." As of May, the Congressional Research Service estimated that Congress has approved $208 billion for the war in Iraq since 2003.

The British, however, had begun focusing on doubts about a postwar Iraq in early 2002, according to internal memos.

A March 14 memo to Blair from David Manning, then the prime minister's foreign policy adviser and now British ambassador in Washington, reported on talks with then-national security adviser Condoleezza Rice. Among the "big questions" coming out of his sessions, Manning reported, was that the president "has yet to find the answers . . . [and] what happens on the morning after."

About 10 days later, Foreign Secretary Jack Straw wrote a memo to prepare Blair for a meeting in Crawford, Tex., on April 8. Straw said "the big question" about military action against Hussein was, "how there can be any certainty that the replacement regime will be any better," as "Iraq has no history of democracy."

Straw said the U.S. assessments "assumed regime change as a means of eliminating Iraq's WMD [weapons of mass destruction] threat. But none has satisfactorily answered how that regime change is to be secured. . . ."

Later in the summer, the postwar doubts would be raised again, at the July 23 meeting memorialized in the Downing Street Memo. Richard Dearlove, then head of MI6, the British intelligence service, reported on his meetings with senior Bush officials. At one point, Dearlove said, "There was little discussion in Washington of the aftermath after military action."

Republican Party Chairman Ken Mehlman, appearing June 5 on "Meet the Press," disagreed with Dearlove's remark. "I think that there was clearly planning that occurred."

The Blair government, unlike its U.S. counterparts, always doubted that coalition troops would be uniformly welcomed, and sought U.N. participation in the invasion in part to set the stage for an international occupation and reconstruction of Iraq, said British officials interviewed recently. London was aware that the State Department had studied how to deal with an invasion's aftermath. But the British government was "shocked," in the words of one official, "when we discovered that in the postwar period the Defense Department would still be running the show."

The Downing Street Memo has been the subject of debate since the London Sunday Times first published it May 1. Opponents of the war say it proved the Bush administration was determined to invade months before the president said he made that decision.

Neither Bush nor Blair has publicly challenged the authenticity of the July 23 memo, nor has Dearlove spoken publicly about it. One British diplomat said there are different interpretations.

Last week, it was the subject of questions posed to Blair and Bush during the former's visit to Washington.

Asked about Dearlove being quoted as saying that in the United States, intelligence was being "fixed around the policy" of removing Hussein by military action, Blair said, "No, the facts were not being fixed in any shape or form at all." He then went on to discuss the British plan, outlined in the memo, to go to the United Nations to get weapons inspectors back into Iraq.

Bush said he had read "characterizations of the memo," pointing out that it was released in the middle of Blair's reelection campaign, and that the United States and Britain went to the United Nations to exhaust diplomatic options before the invasion.