David Letterman to Katie Couric: ‘You Can't Leave the Network, Can You?’ (Video)

Letterman urges her to ride into the sunset at CBS

So this is what the CBS version of peer pressure looks like.

When "CBS Evening News" anchor Katie Couric visited David Letterman's "Late Show" Tuesday, the host let her know that she just can't leave CBS.

Letterman expessed shock that Couric's five-year contract ends after May. Couric said she had "no idea" whether she would take another job. (Several outlets have expressed interest in Couric, a source close to her has told TheWrap.)

"You can't leave the network, can you?" he asked.

"I mean, theoretically yes, it means I could leave the network," Couric said.  (Story continues after the video.)

But Letterman wasn't having it.

"Once you take the anchor chair, that's what you do," he said, to audience applause.

Replied Couric, "Really? Is that a CBS law?"

"No," Letterman said. "But it's It's not like it's a temp gig."

"No," said Couric. "Five years isn't too temporary though."

Letterman then said to look at the examples of Walter Cronkite, Brian Williams, Tom Brokaw, and Peter Jennings. "They get in it they saddle up and they ride into the Sunset," he said. "Into the sunset."

He added that it takes time for viewers to get used to a new anchor, and "you can't just pull the rug out from under the viewers."

Said Couric, laughing: "Okay. Okay, Dave."