David Letterman calls Jay Leno 'insecure' in interview with Oprah Winfrey [VIDEO]

David Letterman's decades-long feud with Jay Leno began in 1992, when the latter maneuvered his way into Johnny Carson's seat at NBC's "Tonight Show," a rivalry so famous it was the subject of the 1996 film, "The Late Shift."

Letterman had a few kind words for his friend-cum-adversary in an upcoming interview special with Oprah Winfrey, but he coupled them with a dig at Leno's supposed "insecurity."

"Jay and I were always friends before all this happened," Letterman begins in the teaser clip.

He's an unusual fellow. I've never met anyone quite like Jay. And I will say, and I'm happy to say, that I think he is 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.

But here's the kicker:

Therefore, the fact that he is also maybe the most insecure person I have ever known -- I could never reconcile that.

Watch the rest of Oprah's interview with Letterman on January 6 at 9/8c on OWN.

Letterman on Leno: "He Is The Funniest Guy I've Ever Known" — First Look