NEW YORK - A source says Jimmy Fallon will officially be given the keys to NBC's "Late Night" franchise following Conan O'Brien's exit.

A person close to the negotiations who spoke on condition of anonymity because the announcement hadn't been made confirmed the widely rumoured change Sunday, saying a news conference is planned for Monday.

All that's left is an official date for NBC's transition - O'Brien moving out West to take over for Jay Leno on the "Tonight" show and Fallon following in the next time slot.

Fallon was a "Saturday Night Live" cast member before leaving for a movie career in 2004.

He has had mixed success, with his most notable role as a childlike Boston Red Sox fan and Drew Barrymore's paramour in "Fever Pitch."

He signed a deal with NBC in 2007 that was widely seen as a way to keep him in the fold until the time came for Monday's announcement.