"Lost" Executive Producer Carlton Cuse told reporters at the Television Critics Association winter press tour Sunday the end date will put a limit on how many more seasons the show will have, and will be announced to fans, TV Week reported.
Producers said setting a firm date for concluding the story about airline passengers marooned on a mysterious island would give fans confidence in the series' narrative.
"It's time for us now to find an endpoint for the show," said Cuse. "J.K. Rowling announced there were seven books in the Harry Potter series and it gives fans (a framework for understanding the arc of the show)."
Ratings for "Lost" have sagged during its third season, but it remains one of ABC's top-rated shows, TV Week said.
Producer Damon Lindelof said the show might top out at 100 episodes, which would take it through the 2008-09 season.
However, ABC Entertainment President Steve McPherson downplayed talk of ending the show, saying "we've had those discussions for the past two years."