American singer Andy Williams says he has been diagnosed with cancer of the bladder.

Williams, 83, broke the news to fans at his Moon River Theater in Branson, Missouri, on Saturday night.

But the singer, famed for songs such as Can't Take My Eyes Off You and Moon River, vowed he would return next year to celebrate 75 years in showbusiness.

Saturday's show was a special Christmas celebration at the theatre, which he built in the town where he also lives.

Williams had to cancel performances at the theatre earlier in the year due to undisclosed health problems.

So when he came on stage early in the show on Saturday, the surprised audience gave him a standing ovation, reported the Branson Tri-Lakes News.

"I do have cancer of the bladder. But that is no longer a death sentence," said Williams, confirming recent press rumours of his illness.

He continued: "People with cancer are getting through this thing. They're kicking it, and they're winning more and more every year. And I'm going to be one of them."

He went on to sing The Christmas Song and said he would be back next September and October to celebrate.

"I'm going to do the shows I've planned to do," he said.

Williams had a string of hits in the 1950s and 1960s, including Can't Get Used To Losing You and Butterfly but he is best known for Moon River.

He also hosted annual Christmas specials on TV and had an Emmy-winning TV variety show in the 1960s called The Andy Williams Show.

Awwww. I love Andy Williams, especially his Christmas albums.  I have such fond memories of listening to his music while decorating the tree.

I wish Andy Williams a speedy recovery.