Dick Van Dyke, 99, gives another surprising secret to a long life after revealing his wife, 54, is key to keeping him young

Dick Van Dyke has detailed the secret to a long life as he approaches his 100th birthday in the coming weeks.

The veteran actor, 99, will reach the massive milestone on December 13 and has lifted the lid on living life to the full in his new novel, 100 Rules for Living to 100.

In the book, Van Dyke goes into detail about his wife, Arlene Silver, 54, who he says has given him a new lease on life.

“Arlene is half my age, and she makes me feel somewhere between two-thirds and three-quarters my age, which is still saying a lot,” he revealed in his new book.

"Every day she finds a new way to keep me up and moving, bright and hopeful and needed."

Van Dyke also spoke on how he 'felt drawn' to Silver when they first met and made a bold first move, sharing that he 'had never approached a strange woman before'.

Van Dyke turns 100 next month (Disney/Randy Holmes)

A smooth-talking Van Dyke penned in an email: "Arlene, I’m afraid I was so smitten with you last night I couldn’t think of anything to say. Still, when the project at Hallmark starts, I’d like to give you a chance to talk with them. Would that be OK?"

The Chitty Chitty Bang Bang star sat down with Today to discuss his new book and reaching 100, where he detailed one of his secrets to living a long life.

And according to Van Dyke, having a sing-along every so often is key.

"Singing is the best thing you can do for yourself," the actor said.

"Usually I wake up with an old tune going through my head my head," he added before going into a verse.

Elsewhere in the Today interview, Van Dyke revealed that he almost ended up playing James Bond.

Initially approached following Sean Connery’s decision to depart from the franchise, Van Dyke recalled: "[Producer] Albert Broccoli came to me and said, ‘Would you like to be Bond?’ And I said, ‘Have you heard my British accent?’ Click!"

Van Dyke did reveal he could have taken the role if he had so wished, but felt it may not have suited what fans had come to expect from him.

At the time, many of his films had been family-friendly movies that could be enjoyed by all ages, so it was the fear of alienating those audiences that ultimately meant Van Dyke decided against taking on the role.