HOLLYWOOD — Heightening fears of an actors strike this summer, one of Hollywood's two major performers unions voted Saturday to break off its 27-year joint bargaining pact with its sister, the Screen Actors Guild, leaving each to negotiate separate new contracts with the major studios.

The 11th-hour move by the American Federation of Television and Radio Artists is the latest thunderclap in Hollywood's winter of discontent, which has seen the television industry upended by a 100-day strike by screenwriters.

It injects a new element of uncertainty in the television and movie industry by raising the possibility of an actors walkout this summer, just as some shows are returning to the air after a three-month absence and the movie industry is trying to get back on its feet. Such a strike could be a further blow to the local economy, already coping with a housing downturn and possible recession.

Hollywood's talent guilds, which represent writers, directors and actors, have pushed to center stage in this year's contract negotiations the issue of how their members are paid in the digital era. Now that directors and writers have reached new three-year contracts with the studios, the industry had hoped the actors could peacefully negotiate a new deal before their contract expires on June 30.

But SAG and AFTRA, the two unions that represent actors, have been at loggerheads over a variety of issues, including each union's contract goals and jurisdictional contests over TV shows. Nonetheless, the two unions have usually been able to set aside their differences long enough to negotiate together on behalf of their members.

Not this time.

AFTRA's move to break off from SAG seemed to be timed for maximum impact, especially given that the two unions had unanimously approved joint proposals for a new film and prime-time television contract that were expected to be presented to the studios in the coming weeks.

A rift between the two unions now could undermine SAG's leverage to wring the best possible concessions from the studios in their new contract as AFTRA, whose members work mostly in television, pursues its own agenda.

At the same time, it could embolden SAG, which has 120,000 members, to call a strike, because its negotiations would be led by the union's hard-liners. They have promised to press for higher residuals for actors from the sale of DVDs, an issue AFTRA has not embraced and one the studios insist is not even on the table.

The current SAG leadership was elected on a platform to "get tough" in negotiations with the studios after a contingent of the membership, dominated by the guild's militant Hollywood faction, thought the previous leadership was too accommodating. AFTRA, which has 70,000 members, is regarded by many as more moderate of the two guilds.

The two unions, which share 44,000 members, have been warily eyeing each other for a long time. The larger SAG is made up exclusively of actors who work in film, television and commercials and has jurisdiction over such popular prime-time series as "Grey's Anatomy" and "Lost." AFTRA, which has its roots in radio, represents local TV anchors, disc jockeys and even recording artists.

The smaller union, however, has growing clout in television; its jurisdiction includes not only game and talk shows but also the booming genre of reality, including "Dancing with the Stars," and is aggressively signing up the casts of cable series, among them such as FX's "Rescue Me."

Roberta Reardon, president of AFTRA, in explaining the decision to negotiate independently, accused SAG of engaging in a "relentless campaign of disinformation and disparagement, culminating in a recent attempt" to wrest jurisdiction of the soap opera "The Bold and the Beautiful" away from AFTRA. Although SAG rejected her claim of interference, Reardon said AFTRA is unable "to have any confidence in their ability to live up to the principles of the partnership and union solidarity."

The studios had invited the guilds to begin joint negotiations as early as this week and were awaiting a response from SAG and AFTRA to set a timeline, which they had hoped to announce Saturday.

But, before the two unions had a chance to sign off on the proposals, AFTRA's board, which met separately Saturday morning in the Century Plaza Hotel, voted to terminate their joint bargaining pact and negotiate the prime-time contract separately.

SAG's leadership, which was holed up all day in the same hotel but in a separate meeting, was stunned by AFTRA's decision and failed in its attempts to get the guild to reconsider its decision.

"It's really tragic," said SAG president Alan Rosenberg. "It's tough enough to compete with the (the Hollywood studios) and try to get fair wages and working conditions for actors. Now we have to compete against our own union. ... What they did today was turn their back on every actor in America."

Over the last year, SAG and AFTRA have feuded over turf and contract terms in cable TV. Tensions boiled over recently when SAG's board urged members to scrap the joint bargaining pact and replace it with one it believed was more equitable. SAG has long resented having to equally share voting power with AFTRA even though the bigger union's members account for the vast majority of earnings each year.

SAG, Hollywood's most powerful union, has also complained that AFTRA has been negotiating cheaper contracts with producers in basic cable television, undercutting SAG's deals. AFTRA's Reardon has blasted SAG's efforts to change the joint bargaining agreement as a violation of the pact and has defended her union's cable deals as fair and in line with those of other unions.

Reardon and SAG's leaders — Rosenberg and national executive director Doug Allen — have traded nasty barbs in the press. Rosenberg has accused AFTRA of wanting to "compete rather than coexist" and Reardon has said her union refuses to "be a silent partner ... relegated to the back bench."

There have been numerous failed attempts over the decades to merge the two unions. In early March, AFL-CIO President John Sweeney met with the leaders of both unions and admonished them to settle their differences.

Although it appeared that the unions had followed Sweeney's advice, tensions were clearly boiling beneath the surface. AFTRA believes SAG is behind a campaign by some actors on the CBS daytime drama "The Bold and the Beautiful" who are petitioning to decertify AFTRA and join SAG because they believe they can get better pay and benefits. SAG denied having any designs to take over soap opera contracts.

The ongoing dispute between the unions has reignited tensions between SAG's Hollywood and New York branches. The New York branch, headed by Sam Freed, is aligned with the moderates in AFTRA. Freed said recently in an interview with the Los Angeles Times that the war between the guilds couldn't come at a worse time.

"The studios will be able to play one union off the other," Freed said.

Some even expect AFTRA and SAG to race to begin negotiations with the studios. Indeed, late Saturday, the Association of Motion Picture and Television Producers, the joint negotiating arm of the studios, said it was happy to "learn" that AFTRA "is ready to begin talks immediately."