Former Vice President Dick Cheney reveals in his memoir that he kept a signed letter of resignation in a safe during his time in office, he told NBC News' Jamie Gangel in an interview airing next week.

In the the much-anticipated book set to be released on Tuesday, Cheney said he had the letter in case he was incapacitated — and that only President George W. Bush and a staffer knew of its existence.

"I did it because I was concerned that - for a couple of reasons," he said. "One was my own health situation. The possibility that I might have a heart attack or a stroke that would be incapacitating. And, there is no mechanism for getting rid of a Vice President who can't function."

Cheney said he has "no regrets" for the use of controversial interrogation tactics like water-boarding, telling Gangel, "I would strongly support using it again if we had a high value detainee and that was the only way we could get him to talk."

In the book Cheney reveals private conversations with Bush, and portrays the 43rd President as less than decisive at times, according to NBC. Cheney said he doesn't think he betrayed Bush's confidence.

Cheney added that he knows the book will make people in Washington angry, saying "there are gonna be heads exploding all over Washington."