Letterman to retire in 'two years,' he says

First, Regis. Now, Dave?

In an apparently unguarded moment during Thursday's interview with Howard Stern, David Letterman dropped this unexpected bombshell: He said he'll leave "Late Show" in two years, when he turns 66.

A slip of the tongue? A joke? Stern was explaining his recent decision to remain with SiriusXM when he abruptly asked Letterman when he planned to retire.

"Two years," was the quick reply. There was no follow-up from Stern, and they moved on to other matters.

Rob Burnett, president of Letterman's production company Worldwide Pants, downplayed the remark in a phone interview. "Dave and Howard are very rare entities in show business in that most people are asked to leave the stage. These guys have complete control over their own exits."

Nevertheless, Burnett said Thursday night's comment was not a formal announcement: "Dave has mused on-air about retiring lots of times. Whenever the day comes that he actually chooses to announce his departure, I don't think that announcement will be ambiguous."

Letterman has mused about retiring on his show. But Thursday was indeed unusual, and perhaps telling.

Letterman turns 64 in April, which means that if he does step down in two years, he would be 66 - the same age his idol and role model, Johnny Carson, left the air.