Former US defense secretary Robert Gates insisted Monday his new memoir is "even-handed" and accused opponents of President Barack Obama of misrepresenting it to score political points.

Gates' book has been widely portrayed as an attack on Obama's war leadership, but the author himself said he had in fact agreed with the major decisions the US president made on Afghanistan.

He told NBC's "Today" show he was "disappointed that the book has sort of been hijacked by people along the political spectrum to serve their own purposes, taking quotes out of context."

And Gates, who served as defense secretary between 2006 and 2011, insisted his memoir, "Duty," was not an attack on the commander-in-chief.

"I think the book is very even handed. I don't vilify anybody," he said.

"I make it clear, I have a lot of respect for both President (George W.) Bush and President Obama," said Gates, who served under both men as Pentagon chief.

He said that "what has been lost in the news media is that I actually agreed with virtually every decision president Obama made" on how to handle the US war in Afghanistan.

But "some people who have a narrative on Obama and the war got out there early with their take on ... what I've written," he told National Public Radio.

The former CIA director, however, made a distinction between Obama and the rest of the White House.

While his criticism of Obama is coupled with praise and respect, Gates makes no apologies for his blunt criticism of Vice President Joe Biden and of the White House staff.

"Well, I had a lot of battles with those folks," he told NPR, referring to members of Obama's national security council staff.

Having worked in the national security council under four previous presidents, Gates said the meddling behavior of the young staff members -- including making calls to four-star generals -- would have constituted "a firing offense" in previous administrations.

Gates also made no effort to back away from his harsh words for the vice president, whom he wrote was wrong about every major foreign policy issue over the past four decades.

The former Pentagon chief said he had long disagreed with Biden on issues dating back to the 1970s.

He said Biden as a senator was wrong to vote against aid for South Vietnam in the 1970s, portrayed the Shah's fall in Iran as a boost to human rights and wrongly opposed the defense build-up under ex-president Ronald Reagan.

"I, frankly, over a long period of time felt that he had been ... wrong," he said.