WASHINGTON — A former White House press secretary, Scott McClellan, defended his bombshell book about the Bush administration yesterday, saying he didn’t speak up against the overselling of war in Iraq at the time because he, like other Americans, gave the president the benefit of the doubt.

“My beliefs were different then. I believed the president when he talked about the grave and gathering danger from Iraq,” McClellan, who was deputy press secretary during the lead-up to the war, told NBC’s “Today” show.

Mr. McClellan, who had worked for Mr. Bush since he was Texas governor, said his initial misgivings about a rush to war were offset by his affection for the president and respect for his foreign policy team. It was easy to believe Mr. Bush, he said, because the president wasn’t consciously trying to inflate the threat of Iraq unleashing weapons of mass destruction.

“He came to convince himself of that,” Mr. McClellan said of Mr. Bush.

In hindsight, Mr. McClellan says he came to view the war as a mistake by a president and advisers swept up in a grand plan of seeding democracy in the Middle East by overturning Saddam Hussein’s regime. Mr. McClellan says Mr. Bush and his aides became so wrapped up in pushing the argument for war that they ignored intelligence that didn’t fit the picture.

Mr. McClellan said he grew “increasingly dismayed and disillusioned” during his final year as White House press secretary, and pinpointed the unfolding of the CIA leak case — and what it disclosed about Mr. Bush’s role in releasing classified information about Iraq to the press — as his tipping point. Mr. McClellan was elevated to press secretary in July 2003 and left the White House in April 2006.

As his book — “What Happened: Inside the Bush White House and Washington’s Culture of Deception” — vaulted to no. 1 on Amazon.com’s best-seller list, Republican critics dismissed him as a turncoat, a sellout, and a disgruntled former employee. The White House called the book puzzling and sad.

A former White House counselor, Dan Bartlett, offered an immediate rebuke to Mr. McClellan’s interview and his allegations of pro-war propaganda.

“I would not personally participate in a process in which we are misleading the American people, and that’s the part that I think is hurting so many of his former colleagues,” Mr. Bartlett said. “To think that he is making such a striking allegation against his former colleagues, to me, is beyond the pale.”

Speaking earlier yesterday to reporters in Sweden, Secretary of State Rice also rejected Mr. McClellan’s allegations that the Bush administration misled the American public.

Ms. Rice would not comment specifically on charges in the book, but said Mr. Bush was honest and forthright about the reasons for the war. She also said she remained convinced that toppling Saddam was right and necessary.