David Letterman to retire as TV host in 2015

David Letterman's guests have included US President Barack Obama

Veteran US late-night TV host David Letterman has announced that he is to retire in 2015.

The star made the surprise statement during a recording of The Late Show with David Letterman on Thursday.

Letterman, 66, is one of the biggest names on US TV. He has spent 21 years hosting the CBS talk show, following 11 years on NBC's Late Night programme.

He said he had told his CBS bosses he would step down in about a year's time, when his current contract expires.

Referring to CBS chairman Leslie Moonves, Letterman told his audience: "I phoned him just before the programme, and I said, 'Leslie, it's been great, you've been great, and the network has been great, but I'm retiring.'"

Letterman thanked "all of the people who have worked here, all of the people in the theatre, all the people on the staff, everybody at home - thank you very much".

Letterman is known for his mixture of big-name interviews and comedy features like his irreverent top 10 lists and segments like Monkey Cam, in which a TV camera was strapped to a monkey while it roamed the studio.

The star began his career as a radio talk show host and local TV weatherman, before becoming part of a comedy troupe on a CBS variety series starring Mary Tyler Moore in 1978.

He was given his own morning programme on NBC show two years later. It only lasted a matter of months, despite winning two Emmy awards.

Late Night with David Letterman followed, and he began to be seen by many as the natural successor to Johnny Carson on The Tonight Show.

Recent guests have included Lady Gaga and Bill Murray

The programme is filmed at the Ed Sullivan Theater in New York

But when he lost that slot to Jay Leno following Carson's retirement in 1992, Letterman moved to CBS and began a long-running rivalry with Leno.

Leno was on top in the ratings for most of their two-decade duel. Letterman's departure comes two months after Leno stepped down from The Tonight Show.

Leno was replaced by Jimmy Fallon, whose show averages 5.1 million viewers a week, compared with 2.9 million for Letterman, according to Nielsen ratings.

CBS chairman Leslie Moonves praised Letterman's "wit, gravitas and brilliance".

He continued: "Dave has given television audiences thousands of hours of comedic entertainment, the sharpest interviews in late night, and brilliant moments of candour and perspective around national events.

"He's also managed to keep many celebrities, politicians and executives on their toes - including me."

Replacement rumours

Jimmy Kimmel, who hosts a rival talk show on ABC, tweeted: "David Letterman is the best there is and ever was."

Speculation has already begun about his replacement, with Craig Ferguson, Jon Stewart, Conan O' Brien, Chelsea Handler and Stephen Colbert among those being tipped.

Lena Dunham, star of the HBO show Girls, tweeted that she hoped CBS would cast a wider net.

She wrote: "I love Letterman but I am really excited about what this could mean for the diversification of late night. Trying not to be a pessimist..."

FIVE CLASSIC LETTERMAN MOMENTS

Letterman took over The Late Show on CBS in 1993

• Madonna seeks to shock

Twenty years ago, Madonna had to be censored after swearing more than a dozen times. She also lit up a cigar and gave Letterman her underwear and invited him to smell it. The episode earned some of the highest ratings of Letterman's career. The host, with his humorous put-downs and refusal to yield to her shock tactics, came out on top.

• Drew Barrymore flashes

With a reputation as a wild child back in 1995, actress Drew Barrymore jumped onto his desk and did a dance before flashing her breasts at the host. "I can't thank you enough for that," Letterman said after he had regained his composure.

• Return after 9/11

His show is not all light-hearted banter. The host delivered a highly-charged and heartfelt opening monologue after the attacks of 11 September 2001. "If you didn't believe it before - and it's easy to understand how you might have been sceptical on this point - if you didn't believe it before, you can absolutely believe it now: New York City is the greatest city in the world," he said.

• Host admits sex scandal

In 2009, Letterman told his audience someone had tried to blackmail him over claims he had affairs with female members of the programme staff. "I have had sex with women who worked on this show," he admitted. "Would it be embarrassing if it were made public? Perhaps it would. Especially for the women."

• Joaquin Phoenix hoax

Also in 2009, actor Joaquin Phoenix appeared incoherent and unrecognisable, with unkempt hair and bushy beard. "Joaquin, I'm sorry you couldn't be here tonight," Letterman quipped. A year later, Phoenix went back on the show to admit it was a stunt for a mock documentary he was making about quitting acting to pursue a hip-hop career.