"Two and a Half Men" may have suddenly shrunk to "One and a Half Men" and the future of CBS' reigning sitcom now hangs in doubt.

Charlie Sheen told CBS and Warner Bros. - which produces the Monday night hit - that he will leave the series after the final episode of the season tapes next Friday, People magazine reported late Thursday, citing a "set source" who said, "Charlie's just done, and he's quietly telling his friends he's not coming back."

CBS declined to comment on the report - standard operating procedure when a story of this magnitude is true, or when a major star is holding them up in negotiations. There were, in fact, online reports late Thursday that said Sheen was seeking a major salary bump.

People did not cite reasons for the resignation, nor suggest Sheen was playing hardball.

His rep, Stan Rosenfield, said via e-mail: "Charlie's deal is only through this current season. That's all I know and that is accurate - that IS all I know."

Sheen has had a tumultuous year, and faces domestic violence charges that stem from a Christmas Day brawl with his wife, Brooke Mueller, which could yield jail time.

He also briefly entered rehab, and abruptly threw the show out of production, forcing it to cut back from 24 to 22 episodes this season, its seventh.

TV comedies are typically more dependent on leading cast members than TV dramas, but "Two and a Half Men" is almost entirely dependent on Sheen, who earns a reported $825,000 per episode or $20 million per year.

"I don't think the show can survive without him," says Brad Adgate, senior vice president/director of research at Horizon Media, a Manhattan-based advertising firm. "It's like Alan Alda leaving 'M*A*S*H' or Ted Danson leaving 'Cheers.' He's too big a part of it."

That of course won't stop CBS from trying to find a new Charlie Harper, or maybe even an entirely new character; too much money is riding on this one.

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Almost as a matter of routine, hit TV series absorb cast defections because they have to - someone may want too much money, or launch a movie career.

Now and then the star simply implodes such as Brett Butler - who battled numerous drug addictions and alcoholism - while on the old ABC hit, "Grace Under Fire," which could not survive her departure.

"Two" is one the rare shows to have survived the vicissitudes of prime time, drawing just about 15 million steady, reliable die-hards every Monday night.

Without "Two," life at CBS will certainly go on - "The Big Bang Theory" and "How I Met Your Mother" have loyal fans, too. But that 9 p.m. gold mine may have just turned into a deep hole.