Casting directors and associates held a press conference in Los Angeles last week to rally industry support for their unionization efforts and to warn studios and networks about a possible work stoppage if their demands are not met.

Labor leaders, casting directors and actors took to the stage, calling for health benefits, a pension fund and collective bargaining status for casting professionals.

Having enlisted the backing of Teamsters Local 399, the modest-size 400-member casting community is suddenly an unexpected political force to contend with as pilot season gets under way this month.

Though studio insiders dismiss worries that casting directors could disrupt the industry, the backing of the North Hollywood Teamsters chapter is causing concern.

“[Casting directors] are not a shut-down-the-town group,” said one key studio source. “You’re talking about a few hundred people. You’re not talking about very much money; you’re talking about the principle of the thing. There is a business downside to having yet another group that can hold you over the barrel because the truck drivers are not going to show up.”

If casting directors participate in a work stoppage, studio sources said, productions will make do.

“Any casting director who decides not to do their job, their jobs will be done by somebody else,” the source said. “In-house employees, producers and directors will talk to agents, like they did in the past.”

But Gary Zuckerbrod, the leader of the unionization effort and casting director on the CBS drama “Without a Trace,” said studios should not underestimate casting professionals’ contribution to the creative process.

“I don’t think the studios have the capacity to cast all the television shows and pilots themselves,” he said. “If they did, they wouldn’t hire us in the first place. Everybody thinks they can do casting. That’s not the reality.”

At stake is decades-old designation that classifies casting directors as independent contractors. Casting directors hire their own staffs, pay for their own health care and sometimes work unpaid for weeks on new shows.

In previous years, casting directors approached the Directors Guild of America and the Screen Actors Guild seeking bargaining alliances, only to be rebuffed.

But in December they struck a deal with the International Brotherhood of Teamsters, which agreed to represent their interests in return for casting directors adding their above-the-line weight to Local 399-which also represents drivers, animal handlers, location scouts and prop masters.

Though previous attempts to unionize have ended in failure, this time casting directors are finding momentum in their favor as Hollywood luminaries and media reports express shock at the apparent second-class-citizen status bestowed on an integral part of the production team. Almost every crew member in Hollywood-from actors to craft services-is represented by one union or another.

The DGA, SAG and the Writers Guild of America have filed motions of support, along with dozens of actors, producers and directors.

“Casting directors must be afforded the same benefits that other key crew members are afforded,” “Lost” showrunner J.J. Abrams wrote in a statement. “It’s bizarre that this is even an issue.”

One reason for the surprise is the Casting Society of America. Many assume the “C.S.A.” designation following the name of casting directors in production credits indicates a representative organization. But the CSA is instead an honorary society, of which Mr. Zuckerbrod was formerly president.

Actress Marcia Gay Harden, taking the stage at the union organizers’ press conference, said the lack of benefits and studio resistance is “shameful, shocking and appalling.”

“It’s a bit of a surprise that there is such a vehement opposition [to the union],” she said. “It’s fear that one more person on the boat might sink it.”

A spokesperson for the Alliance of Motion Picture and Television Producers said studios are irked by union organizers’ efforts to paint the producers as unwilling to provide basic benefits.

“We want to make sure people know that on Jan. 24 the studios met with the casting directors and offered them the means to find pension and health care coverage for them,” spokeswoman Barbara Brogliatti said. “They turned that down.

Not true, countered Mr. Zuckerbrod. “They did not offer health and pension, they offered `exploration’ of health and pension, which we took to be a stalling tactic,” he said.

Both sides agree the AMPTP is probably willing to provide such benefits, however. The question is how. The AMPTP would prefer to put casting directors on the studio or network health-care and pension plans. Casting directors want such benefits plus union protection.

Though the casting directors’ list of demands represents a rather sweeping change in their status they are not looking to get DVD residuals, Mr. Zuckerbrod said.