Late Show host David Letterman has said he will retire next year.

During a taping of today's show, Letterman said he has informed his CBS bosses that he will step down in 2015, when his current contract expires.

He told his audience that he expects his departure will be "at least a year or so" from now.

Letterman turns 67 next week. He has the longest tenure of any late-night talk show host in US television history, nearing 32 years since he created Late Night at NBC in 1982.

He moved to CBS to start Late Show in 1993.

Jay Leno, his rival to host NBC's Tonight Show, retired earlier this year, making way for Jimmy Fallon.