UPDATE 6-Hollywood writers start strike after talks collapse

(Adds quotes, details from California pickets)

By Steve Gorman

LOS ANGELES, Nov 5 (Reuters) - Some 12,000 screenwriters went on strike against the U.S. film and television industry on Monday after the collapse of last-ditch contract negotiations aimed at preserving nearly 20 years of Hollywood labor peace.

Ten hours of bargaining presided over by a federal mediator failed to close a deal before a strike deadline set last Friday by the Writers Guild of America, which has sought a greater share of DVD and Internet revenues for its members.

The initial impact of a strike for most of the public will be felt on television.

Popular late-night talk shows such as NBC's "The Tonight Show With Jay Leno" and CBS' "Late Show With David Letterman," which are produced on a day-to-day basis and depend on a steady supply of topical jokes and sketches, were expected to go into immediate reruns.

Prime-time comedies such as the CBS hit "Two and a Half Men" and Kelsey Grammer's new Fox sitcom "Back to You" also are expected to be knocked out of production because they depend on a substantial amount of last-minute script rewrites.

The effect on movies will be less obvious since the major studios' screenplay pipeline is well-stocked through 2008.

Even as talks in Los Angeles had dragged on late on Sunday, the union's East Coast branch declared it was going ahead with the walkout at 12:01 a.m. EST, and the larger West Coast contingent joined the work stoppage three hours later.