PHOENIX — President Bush "convinces himself to believe what suits his needs at the moment" and has engaged in "self-deception" to justify his political ends, Scott McClellan, the former White House press secretary, writes in a critical new memoir about his years in the West Wing.

In addition, McClellan writes, the decision to invade Iraq was a "serious strategic blunder," and yet, in his view, it was not the biggest mistake the Bush White House made. That, he says, was "a decision to turn away from candor and honesty when those qualities were most needed."

McClellan's book, "What Happened: Inside the Bush White House and Washington's Culture of Deception," is the first negative account by a member of the tight circle of Texans around Bush. McClellan, 40, went to work for Bush when he was governor of Texas and was the White House press secretary from July 2003 to April 2006.

The revelations in the book, to be published by PublicAffairs next Monday, were first reported on Tuesday on Politico.com by Mike Allen. Allen wrote that he bought the book at a Washington store. The New York Times also obtained an advance copy.

McClellan writes that top White House officials deceived him about the administration's involvement in the leaking of the identity of a CIA operative, Valerie Wilson. He says he did not know for almost two years that his statements from the press room that Karl Rove and I. Lewis Libby Jr. were not involved in the leak were a lie.

"Neither, I believe, did President Bush," McClellan writes. "He too had been deceived, and therefore became unwittingly involved in deceiving me. But the top White House officials who knew the truth — including Rove, Libby, and possibly Vice President Cheney — allowed me, even encouraged me, to repeat a lie."

He is harsh about the administration's response to Hurricane Katrina, saying it "spent most of the first week in a state of denial" and "allowed our institutional response to go on autopilot." McClellan blames Rove for one of the more damaging images after the hurricane: Bush's flyover of the devastation of New Orleans. When Rove brought up the idea, McClellan writes, he and Dan Bartlett, a top communications adviser, told Bush it was a bad idea because he would appear detached and out of touch. But Rove won out, McClellan writes.

A theme in the book is that the White House suffered from a "permanent campaign" mentality, and that policy decisions were inextricably interwoven with politics.

McClellan does not exempt himself from failings — "I fell far short of living up to the kind of public servant I wanted to be" — and calls the news media "complicit enablers" in the White House's "carefully orchestrated campaign to shape and manipulate sources of public approval" in the march to the Iraq war in 2002 and 2003.

He does have a number of kind words for Bush, particularly from the April day in 2006 when Bush met with McClellan after he learned he was being pushed out. "His charm was on full display, but it was hard to know if it was sincere or just an attempt to make me feel better," McClellan writes. "But as he continued, something I had never seen before happened: Tears were streaming down both his cheeks."