Sen. John McCain in his new memoir makes the confession that the Iraq War was a "mistake" and says he shoulders part of the blame, Vox reported Friday.

He explained the Iraq War "can't be judged as anything other than a mistake, a very serious one, and I have to accept my share of the blame for it."

McCain was a steadfast supporter of the initiative to go to war with Iraq during the administration of former President George W. Bush.

"I came out of the Vietnam War convinced that frankly we could have won, and we had it won," Politico's Michael Hirsh said the Arizona Republican told him in 2014. "Just as I believed we had the Iraq conflict won after the surge — and for which I sacrificed everything, including my presidential ambitions, that it would succeed."

Even back in 2005, when 66 percent of the country was against the effort to bring democracy to Iraq, McCain doubled down on his support of the war.

"Securing ever-increasing parts of Iraq and preventing the emergence of new terrorist safe havens will require more troops and money," McCain said at the time at an event with the American Enterprise Institute. "It will take time, probably years, and mean more American casualties. Those are terrible prices to pay. But with the stakes so high, I believe we must choose the strategy with the best chance of success."

Estimates are that the Iraq War resulted in 150,000 to 460,000 casualties and contributed to a continuing instability in the region.

McCain's memoir, entitled "The Restless Wave: Good Times, Just Causes, Great Fights, and Other Appreciations," was released earlier this week where the longtime senator reflects on his life. Currently battling brain cancer, McCain said he wrote it because he had "some things I’d like to take care of first, some work that needs finishing, and some people I need to see. And I want to talk to my fellow Americans a little more if I may."