By Dean Goodman

LOS ANGELES (Reuters) - Hollywood screenwriters said on Thursday they will go on strike for the first time in two decades after failing to renew their contract with producers, a move that could fill U.S. TV screens with reruns and reality shows.

Writers Guild of America officials told an estimated 2,000 union members during a closed meeting that they will announce plans on Friday, following a meeting of the executive boards of the union's East and West Coast branches.

Reports suggested that writers, who are demanding a bigger cut of DVD and Internet revenues, could down pens and form picket lines as early as Monday.

Union officials were not available for comment, but members said a strike was inevitable.

"There's an impasse and there's no progress," said comedy writer David Garrett. "It's about all we can do."

The producers alliance, which fiercely resisted writers' demands for higher residual payments for DVD sales and Internet downloads, said in a statement that it was "ready to meet and ... prepared to close this contract this weekend."

A lengthy strike will impact television programming and movie production, although Hollywood studios have been stockpiling scripts in the event of a stoppage.

The late-night talks shows will go off the air almost immediately since they rely on a daily supply of topical jokes. The prime-time schedules will start filling up with more reruns and game shows after the networks have burned through fresh episodes. The new shows fighting to hold viewers' attention in the first few weeks of the new season face a grim future if they have to leave the schedule for an extended period.

The WGA's three-year contract, covering 12,000 movie and TV writers, expired early on Thursday. Union leaders won approval two weeks ago from members to call a strike if deemed necessary once the contract expired.

The WGA and the Alliance of Motion Picture and Television Producers, which have been negotiating since July, brought in a federal mediator this week to try to break the deadlock on the key issue of remuneration in the digital age.

The studios have said union demands for higher residuals on DVDs and Internet downloads would stifle growth at a time of rising production costs, tighter profit margins and piracy threats. They insist that digital distribution of movies and TV remains largely experimental or promotional and new-media business models are just developing.

The union accuses the studios of pleading poverty and argues that writers have never gotten a fair deal on the lucrative DVD industry. They also see more of film and TV migrating toward the Internet and wireless platforms and want a bigger piece of that revenue pie.

The last major film and television strike was a WGA walkout in 1988 that lasted 22 weeks, delayed the start of the fall TV season and cost the industry an estimated $500 million. The motion picture and TV industry generates $30 billion in annual economic activity for Los Angeles County alone.

(Additional writing by Steve Gorman)