Washington, Aug. 25: Former U. S. vice-president Dick Cheney kept a secret resignation letter locked away in a safe in case he were ever to be incapacitated, he reveals in his new book.

The letter, which Cheney signed in March of 2001, was written because of his health.

"The possibility that I might have a heart attack or a stroke that would be incapacitating. there is no mechanism for getting rid of a vice president who can't function," he told NBC in an interview that will air Monday as the book is published.

The letter was locked in a safe at all times - the location was not disclosed in the interview - and known only to a handful of people, including President George W. Bush.

Cheney did the interview as part of the promotion for his upcoming memoir, "In My Time," which hits the shelves August 30.

Cheney admitted that contents of the book could have an exploding effect all over Washington. (ANI)