The odds of a strike by casting directors and associates has risen several notches with a strong pledge of support from a top official of the Teamsters union.

James P. Hoffa, general president of the Intl. Brotherhood of Teamsters, has warned studios and networks that his union will provide backing for a possible work stoppage by about 500 casting directors and associates in Hollywood and New York if they are not allowed to unionize. And he offered to intervene in the negotiations.

“The purpose of this letter is to advise you that the Intl. Union is in full support of this effort and will provide whatever assistance is necessary to accomplish the goal of achieving a fair and equitable bargaining agreement for these deserving employees,” Hoffa wrote in a letter sent Tuesday to Nick Counter, president of the Alliance of Motion Picture & Television Producers.

Hoffa’s letter amps up the pressure on studios and nets, which are also facing the prospect of a work stoppage by actors this summer. SAG and AFTRA walked away from the bargaining table without a deal on Sunday and, although the actors’ union film-TV contract doesn’t expire until June 30, no new talks have been set.

Should a SAG-AFTRA deal not emerge in the next few weeks, the uncertainty of an unresolved contract will trigger more production in the coming weeks to withstand a work stoppage this summer.

The Teamsters have been attempting to unionize the casting directors and associates — one of the most significant non-union groups of employees in Hollywood — for two years. Teamsters Local 399 has indicated in recent months that a work stoppage will follow if the AMPTP doesn’t grant recognition to the Teamsters as a bargaining unit for the casting directors and associates.

Counter warned the Teamsters last month of upcoming legal challenges if it persists in planning for a strike, asserting that most casting directors are independent contractors rather than employees. He said that any attempt to combine in an effort to affect the prices paid for their services is unlawful under federal antitrust laws and a wide variety of state laws.

Hoffa disputed Counter’s contentions in his letter.

“The Intl. Union respectfully disagrees with your assessment and will support these employees in their attempt to gain recognition and a contract,” Hoffa said.

Hoffa also said he was puzzled by Counter’s stance.

“Apparently the producers fail to understand that the cost of potential litigation or even a job action would far exceed what it would take to secure an agreement,” he said.

Reps for the AMPTP were not available for comment Tuesday.

The Teamsters have secured support for the organizing initiative from other Hollywood unions, including SAG, WGA, DGA and AFTRA. Local 399 also represents 4,100 studio drivers, location managers and location scouts.