Former US Defense Secretary Donald Rumsfeld concludes in his new autobiography that the war in Iraq has been worth the cost and remains largely unapologetic about his handling of the conflict, The Washington Post reported on Wednesday.

Had the government of Saddam Hussein remained in power the Middle East would be "far more perilous than it is today," Rumsfeld wrote in his 800-page memoir, scheduled for release on Tuesday.

Rumsfeld and other US officials cited the threat posed by Iraqi weapons of mass destruction as justification for the 2003 US-led invasion. No such weapons were found.

The former defense chief was a leading architect of the Iraq war. He was fired by President George W. Bush in 2006 with US troops bogged down after 3-1/2 years of fighting in Iraq.

Rumsfeld's book "Known and Unknown," a copy of which was obtained by The Washington Post, covers his entire life, but more than half deals with his six years as Bush's defense chief.

Speaking out for the first time since leaving office, Rumsfeld offers a vigorous explanation of his own thoughts and actions about the war and is making available on his website (www.rumsfeld.com) many previously classified or private documents, the Post reported.

Much of Rumsfeld's explanation of what went wrong in the crucial first year of the occupation of Iraq stems from a pre-war failure to manage the post-war political transition when the State Department and Pentagon held vastly different views, the newspaper said.

Rumsfeld depicts Bush as presiding over a national security process that was marked by incoherent decision-making and policy drift, a detriment to the war effort, the Post said.

Rumsfeld suggests that Bush was at fault for not doing more to resolve disagreements among senior advisers.

Bush "did not always receive, and may not have insisted on, a timely consideration of his options before he made a decision, nor did he always receive effective implementation of the decisions he made," Rumsfeld wrote.

Addressing charges that he failed to provide enough troops for the Iraq war, the former defense chief wrote: "In retrospect, there may have been times when more troops could have helped."

But Rumsfeld insists that if senior military officers had reservations about the size of the invading force, they never informed him, the Post said.

In a lengthy section on the administration's treatment of wartime detainees, Rumsfeld regrets not leaving office in May 2004, after the Abu Ghraib prison scandal erupted, The Washington Post said.

"Looking back, I see there are things the administration could have done differently and better with respect to wartime detention," Rumsfeld acknowledges.