NEW YORK -- After 25 years, ABC News' "Nightline" is about to learn whether there is life after Ted Koppel.

Or is it?

The much-honored late-night news program will lose the only anchor it has ever had at the end of the year. Koppel said Thursday he will end his 42-year career when his contract expires in December.

ABC News president David Westin and the "Nightline" staff want the show to go on. They're confident it will. But the ultimate decision rests with top ABC executive Anne Sweeney and the parent Walt Disney Corp.

ABC's secret courtship of David Letterman three years ago proved ABC isn't wedded to the idea of news in the 11:35 p.m. time slot. But with stars like Conan O'Brien and Jon Stewart locked into long-term contracts, and ABC's Jimmy Kimmel not burning up the ratings, there may not be a strong entertainment option at that hour.

ABC cousin ESPN could be tapped to propose alternative programming that would be attractive to young male viewers, but the trick is to do it without hurting ESPN.

Longtime "Nightline" executive producer Tom Bettag, who's leaving with Koppel at the end of the year, said he's "really pretty bullish" about the news show's future.

Westin is immersed in planning for it, working under the assumption the show will continue. He wants "Nightline" to expand to an hour, and be shown live five nights a week. He's tested ideas at ABC's Times Square studio, and "Nightline" staff in Washington have presented him with a proposal to keep the show there.

"I think the chances are very good, provided we continue to do a high-quality broadcast that continues to draw viewers," Westin said. The show averages just under 4 million viewers this year, down from 6.3 million a decade ago.

Koppel, 65, was given the option of staying at ABC News under two scenarios that ultimately proved undesirable.

Lately he's been anchoring the program three nights a week, often taping it in the late afternoon. Going live late at night, for an hour five times a week, is a significantly tougher workload he doesn't want to take on at this point.

ABC had also discussed switching Koppel with "This Week" host George Stephanopoulos, but moving to the third-rated Sunday morning political talk show held little appeal to Koppel.

So after returning from a long vacation this week, Koppel informed Westin that he was ready to leave.

Koppel said Westin has assured him that he was not being pushed out the door.

"But who knows?" Koppel said. "Maybe it was. I'm too much a reporter and a realist, and have been in this business too long, not to recognize that my salary is very high, particularly for someone who only does three days a week now."

"Nightline," originally anchored by Frank Reynolds, began as a series of special reports during the Iranian hostage crisis in November 1979. Then ABC News president Roone Alredge seized on the opportunity to wrest the time from affiliates, and it became a regular newscast the following March.

Koppel's use of technology to conduct live interviews with subjects all around the world and show remote shots from far-flung places like Mount Everest -- now television staples -- were groundbreaking when "Nightline" started.

He also said he's proud of the show's efforts to investigate subjects that often didn't get much attention on television, such as the criminal justice system. "Nightline" did some 40 shows on the AIDS crisis over the years, he said.

Koppel had been ABC News' chief diplomatic correspondent for the decade before "Nightline" began. He joined ABC News as a general assignment reporter in New York at age 23 in 1963.