For the first time in the history of "The Late Show," a sitting president is coming to visit David Letterman.

CBS has announced that President Barack Obama will have a sit-down on the Monday, Sept. 21 episode of "Late Show with David Letterman."

Not surprisingly, President Obama will be the only guest on the Monday show.

While this will be Obama's first "Late Show" appearance as president, he's made six previous visits, mostly recently on Sept. 10, 2008. President Obama has been spending more time in primetime lately, including an address to Congress last Wednesday which preempted programming on NBC, CBS and ABC.

It's a big "get" for "The Late Show" and the latest blow in what has already been a difficult morning for Letterman's after-hours rival Conan O'Brien. In addition to watching his own ratings slide opposite Letterman's, O'Brien had to wake up to news of Jay Leno's 17.7 million viewer primetime debut.

"The Tonight Show with Conan O'Brien" has yet to announce its guests for the Monday show.