Former US defence secretary Donald Rumsfeld said his biggest mistake during his six years in the Pentagon was not resigning after shocking photos of the treatment of Iraqi inmates by American soldiers at Baghdad's Abu Ghraib prison were published.
The New York Times and The Washington Post published articles about Mr Rumsfeld's forthcoming autobiography, Known And Unknown, based on copies they obtained before its release next Tuesday.
In the book, Mr Rumsfeld said he submitted his resignation to President George Bush twice in 2004, five days apart, after the misconduct of soldiers at Abu Ghraib became public. Mr Bush rejected both but finally removed Mr Rumsfeld from the Cabinet after elections in 2006.
The Washington Post quotes Mr Rumsfeld as saying in the book: "More than anything else I have failed to do, and even amid my pride in the many important things we did accomplish, I regret that I did not leave at that point."
Mr Rumsfeld, 78, also criticised the Bush administration for failing to work with the US Congress on the treatment of prisoners.
"Looking back, I see there are things the administration could have done differently and better with respect to wartime detention," he said.
The accounts of the book also quote Mr Rumsfeld as criticising both of Mr Bush's secretaries of state, General Colin Powell and later Condoleezza Rice.
He accused Ms Rice of putting democracy and human rights before US security. But Mr Rumsfeld had particularly harsh words for Paul Bremer, who took charge in Baghdad, saying he did not keep the Pentagon informed of his intentions even though the defence secretary was his boss.