David Letterman called his old rival Jay Leno "the funniest guy I've ever known"-- and also the "most insecure" -- in a back-handed compliment-laced interview with Oprah Winfrey on her OWN program "Oprah's Next Chapter."
In a promotional clip posted online, Letterman explained to Winfrey why the two nighttime-talk personalities lock horns -- and he said it's not because Leno got the treasured post-Johnny Carson "Tonight Show" gig.
"He's an unusual fellow -- I've never met anyone quite like Jay," Letterman, seated next to Winfrey, said in the video. "And I will say, and I'm happy to say, that I think he's the funniest guy I've ever known. Just, flat out, if you go to see him do his nightclub act, just the funniest, the smartest, a wonderful observationist and very appealing as a comic."
Then, he hit home: "Therefore, the fact that he is also maybe the most insecure person I have ever known -- I could never reconcile that."
The interview will air on OWN on Jan. 6.
Here's the clip: