And the feud goes on.

David Letterman** and Jay Leno** have been locked in a highly publicized rivalry for two decades now -- ever since Leno was named Johnny Carson's Tonight Show replacement over Letterman, who left NBC for CBS as a result of the snub. The battle between the two comedians is so famous that it was the subject of a 1996 HBO film, The Late Shift. But Letterman claims that their fallout is more complicated than some 20-year-old spat over a job.

In a new teaser for his sit-down with frenemy Oprah Winfrey** -- with whom he had a 16-year feud beginning in 1989 -- Leno's rival opens up about his much-discussed relationship with his fellow comic and former pal. (The full Oprah's Next Chapter interview airs Jan. 6 on OWN.)

"We were always friends before all of this happened," the Late Show host, 65, tells Winfrey. "He has a way...he's an unusual fellow. I've never met anyone quite like Jay."

He goes on to add that despite their feud, he thinks Leno is "the funniest guy" he's ever known. "If you go to see him do his nightclub act, [he's] just the funniest, the smartest, a wonderful observationist, and very appealing as a comic," Letterman says.

High praise -- but there's a "but."

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

Tell Us: Are you Team Leno or Team Letterman?

This article originally appeared on Usmagazine.com: David Letterman: Jay Leno Is "the Most Insecure Person I Have Ever Known"