Four US presidents have joined stars including Steve Martin, Tina Fey, Jerry Seinfeld and Foo Fighters to pay tribute to TV host David Letterman on his final late night talk show.

Letterman has bowed out after 33 years and 6,028 late-night broadcasts.

His final broadcast began with pre-recorded clips of former US presidents George H and George W Bush and Bill Clinton echoing fellow ex-president Gerald Ford's post-Watergate remark that "our long national nightmare is over".

Barack Obama then appeared to repeat that statement before adding: "Letterman is retiring." The host then joined him to ask: "You're just kidding, right?"