Writers walk the picket line along with other members of the Writers Guild of America at the main gate to Walt Disney studios in Burbank, California Nov. 5, 2007. Some 12,000 screenwriters went on strike against the US film and television industry on Monday after the collapse of last-ditch contract negotiations aimed at preserving nearly 20 years of Hollywood labor peace. - Xinhua/Reuters

Prominent politicians, celebrities and actors are either endorsing striking writers or joining the picket lines in Los Angeles and New York.

Motorcyle riding "Tonight Show" host Jay Leno delivered doughnuts Monday to striking writers at NBC, while Julia Louis-Dreyfus marched with pickets at Warner Bros. in the shadow of a giant billboard advertising her CBS show, "The New Adventures of Old Christine."

Louis-Dreyfus wore a cap, sunglasses and Screen Actors Guild T-shirt as she joined strikers chanting, "Hey, hey, pencils down. Hollywood's a union town."

"How this is resolved will directly affect our union, too," she said, referring to the actors union contract that expires next year.

In New York, Tina Fey of "30 Rock" joined strikers outside Rockefeller Center, the headquarters of NBC.

Even Democratic presidential candidates weighed in Monday. Barack Obama said he stands with the writers and urged producers to work with them to end the strike, and Hillary Rodham Clinton called for a contract that recognizes the contributions writers make to the entertainment industry.

Each candidate has received more than US$2 million in campaign contributions from the entertainment industry.

Strikers near Universal Studios marched across a freeway bridge and waved signs at passing motorists. Outside the landmark gate of Paramount Pictures on Melrose Avenue, drivers honked their horns in solidarity with strikers.