Newman's career as an actor has spanned more than five decades

Newman, a nine-time Oscar nominee who has starred in more than 50 films, claimed he was no longer able to perform to the best of his ability.

"I'm not able to work anymore... at the level that I would want to," the actor said in an interview on US television.

Newman's films include The Sting, Cool Hand Luke and The Color of Money, which earned him a best actor Oscar in 1987.

Newman announced his decision in an interview with US broadcaster ABC.

"You start to lose your memory, you start to lose your confidence, you start to lose your invention," he told ABC's Good Morning America.

"So I think that's pretty much a closed book for me."

Charity work

Newman's career on stage and screen has spanned more than five decades.

One of his biggest hits was the 1969 Western Butch Cassidy and the Sundance Kid, in which he starred with Robert Redford.

The pair joined forces again in 1973 playing con men in The Sting.

Recent projects have included 2002's Road to Perdition, earning Newman another Oscar nomination, and the TV mini-series Empire Falls, for which he won an Emmy.

In recent years, the Ohio-born star has also set up a successful food business.

Profits from his food production company are donated to charity, while the actor has helped establish a number of camps for critically ill children.

He has been married to actress Joanne Woodward since 1958.