Chuck Todd taking over for David Gregory at NBC's "Meet the Press"

Embattled "Meet the Press" moderator David Gregory is leaving NBC News and Chuck Todd will replace him on the venerable Sunday morning public affairs program.

Todd begins his new role on Sept. 7. He will remain as NBC News' political director, but will relinquish his duties as chief White House correspondent and anchor of MSNBC's "The Daily Rundown," NBC announced Thursday.

Gregory, who has hosted the Sunday morning public-affairs program since 2008, had been with NBC News since 1995.

The announcement by NBC News president Deborah Turness confirmed months of speculation that Gregory's time was running out on the program, which during his tenure dropped from first place to third in the ratings.

In April, Turness was moved to defend Gregory in a statement of support "for the show and for David, now and into the future...."

The official word followed by a couple of hours a Twitter post by Gregory himself that he is departing: "I leave NBC as I came -- humbled and grateful," he said.

NBC News correspondent Andrea Mitchell will serve as moderator this weekend.

"Meet the Press," which premiered in 1947, is the longest-running network show on TV.