The long-simmering standoff between hotel workers and management boiled over Tuesday as unionized employees marched through downtown and staged a sit-in in the lobby of the San Francisco Hilton.

The workers, including Local 2 President Mike Casey, infiltrated the hotel before management had an opportunity to erect barricades and blockade nonhotel guests from entering. Inside the hotel lobby, hotel workers sat on the steps descending into the sunken lobby, chanting, "What do we want? Contract!"

Police took 37 protesters into protective custody as about 500 Local 2 members and supporters stood outside cheering their fellow workers and yelling "shame on you" at hotel guests entering the Hilton.

The demonstration comes as negotiations have sputtered to a halt between the 4,300-member Local 2 UNITE HERE and the 14-hotel San Francisco Multi-Employer Group. The two sides, which agreed to a "cooling-off period" last November after a two-week strike and a six-week lockout, have not met since Feb. 14; disagreements remain over health care, wages, pensions, and length of contract.

Local 2 Vice President Lamoin Werlein-Jaen said Tuesday's civil disobedience was an effort to "unclog things and demonstrate that we're just as determined as we were last fall to get a fair contract."

The owners group, known as SFMEG, condemned the action, calling it "unlawful," and "disruptive."

"It is also indicative of the total disinterest of Local 2 leadership to engage in productive negotiations," said the statement.

While the hotel owners say they have made significant concessions on all the key talking points, the union argues the owners have still not responded to their last proposal, made on Jan. 21. Meanwhile, the union is engaged in an aggressive boycott of the 14 hotels and have thus far convinced two large conventions - the Organization of American Historians and the American Anthropological Association - to move their meetings out of San Francisco.

On Tuesday, Chamber of Commerce CEO A. Lee Blitch blasted the union in an editorial, calling the boycott tactic "a strike that is not a strike."

Hilton Hotel guests, who currently include 1,600 librarians and hundreds of independent filmmakers in town for a gathering of the San Francisco-based Independent Television Service, mostly took the workers side.

Lyn Goldfarb, a Los Angeles-based documentary filmmaker said organizers tried to cancel their contract with the Hilton, but would have lost $600,000. She said she was boycotting events at the hotel and that many seminars had been moved elsewhere.

"A lot of us are upset," she said. "We think the hotel is wrong not to let the conference out of the contract."

One Portland librarian, who did not give her name, said she had been assured that "there wasn't a strike and we would not be crossing a picket line."

"If this is not a picket line then I don't know what one is," she said.

Susan Donahue, a cook at the Hilton and a member of the union negotiating team, said the "uncertainty" of the ongoing dispute was "trying," but she was disinclined to give in.

"We have to show them it will cost them more to fight than to settle," said Donahue.