Colin L. Powell, who as secretary of state famously made the case for war against Iraq in 2003 with an impassioned speech at the U.N. Security Council, was more skeptical about the evidence he used to justify the U.S.-led invasion than previously known, according to a new memoir by Kofi Annan, the secretary-general at the time.

Six weeks after the Iraq invasion, Annan wrote, Powell visited his 38th-floor office at the United Nations to privately exult with him over news that U.S. forces believed they had found mobile laboratories in Iraq that the administration claimed were used by Saddam Hussein to make weapons of mass destruction — the core reason for the war.

“Kofi, they’ve made an honest man of me,” Annan quoted Powell as telling him.

Annan wrote that “the relief — and the exhaustion — was palpable. I could not help but smile along with my friend, and wanted to share in his comfort,” even though Annan himself was far from convinced. Still, Annan wrote, “I could only be impressed by the resilience of this man, who had endured so much to argue for a war he clearly did not believe in.”

Efforts to reach Powell for comment about the passage were not immediately successful. Peggy Cifrino, his office assistant, said he was traveling and contacting her only intermittently.

By now, of course, many books have been written on the run-up to the Iraq War, in which no weapons of mass destruction were ever found. Powell’s role, which some historians say irreparably harmed his credibility and derailed his political career, has also been well documented.

But the encounter between Powell and Annan, as reprised by the former secretary-general, offered a new insight into the degree of doubt harbored by Powell about putting troops on the ground in Iraq.

In a telephone interview from his Geneva office, Annan, 74, said he had decided to use that anecdote in the opening chapter of his new book, “Interventions: A Life in War and Peace,” published by The Penguin Press, because Iraq had been such an important issue during his tenure, which lasted from 1997 through the end of 2006. The Iraq War, he said, was “an event that divided the international community hopelessly — the way Syria is about to do.”

Moreover, Annan said, he regarded Powell as “a friend, highly respected, a star among the foreign ministers. And I think the presentation of the U.S. case to the council did a bit of harm to him, and I wanted to convey what happened at the time.”

The 383-page book, written in collaboration with Nader Mousavizadeh, Annan’s former adviser and speechwriter, is a chronicle of his diplomatic life. Born in Ghana, Annan is the first career U.N. official and first sub-Saharan African to rise to the post of secretary-general. He was awarded the Nobel Peace Prize in 2001 for his work at the U.N.

Written as part autobiography, part history lesson, it is infused with Annan’s accounts of private encounters with world leaders, including Saddam, with whom he once had an intense exchange in Baghdad, persuading him to allow weapons inspectors into Hussein’s presidential palace.

The book is also Annan’s effort to explain the circumstances behind some spectacular lapses that have been partly attributed to Annan during his tenure as secretary-general and earlier, when he ran the department in charge of U.N. peacekeeping operations.

Annan wrote that the reasons behind the U.N. failure to avert the 1994 Rwanda genocide, to take one example, were rooted in earlier peacekeeping debacles in Somalia and Haiti. Many nations that had contributed peacekeepers, led by the U.S., developed an aversion to taking such risks, Annan wrote, and the Security Council resisted ordering measures that might include the use of force.

“Fatefully, the first operation to be created in this climate was the mission to Rwanda.”

In what may be a surprise to some of Annan’s conservative critics, he expressed great admiration in the book for President George W. Bush, despite their disagreements on the Iraq War and what Annan regarded as Bush’s flawed approach to the Israeli-Palestinian conflict. Annan said Bush’s effort to combat the global AIDS epidemic represented “the biggest financial commitment by any country in history to fight a single disease.”

Annan said he had been working on the memoir for two years and was nearly finished this past winter when he got a telephone call from Ban Ki-moon, his successor as secretary-general, with an extraordinary request.

Ban wanted Annan to negotiate a diplomatic solution to the Syria uprising, as a special envoy representing the U.N. and the Arab League, where exasperation with President Bashar Assad of Syria seemed intractable.

Ban said he was asking on behalf of a group of foreign ministers, who believed that Annan’s negotiating skills could succeed in Syria.

Annan, who had dealt with Syria’s president before, consented, and the book was delayed, with the final pages to be revised.

“We had been on the verge of delivering it to the editors,” Annan said.

The Syria portion of the book, which goes on sale Sept. 4, was updated to include a tenuous cease-fire that Annan negotiated in March. But Annan is no longer the special envoy, having resigned in frustration in early August as the cease-fire was ignored.

Since then, the conflict has worsened. The 300 U.N. monitors who were to observe his cease-fire have left Syria, and a new special envoy, Lakhdar Brahimi, who once worked for Annan, has now been designated his successor.

Still, Annan said, he had decided awhile ago that he would make no further revisions to the book.

Now, he said, “people are asking me if I’ll write a second book, about Syria.”

Annan said that in his multiple meetings with Assad in Damascus, he felt that he never got through to him. “Initially I felt he was in denial,” Annan said. “He felt like most of his problems were being caused by outsiders. If outsiders were to leave Syria alone, they would resolve their problems in no time.”

Leaders like Assad, he said, “tend to believe in the world they create.”

© 2012 The New York Times Company