By Steve Gorman

LOS ANGELES (Reuters) - An insurgent faction within the Screen Actors Guild has launched a campaign to wrest control of the powerful union from leaders they blame for stalemated contract talks with major Hollywood studios.

A bloc of SAG members calling itself Unite for Strength unveiled a slate of 31 candidates on Wednesday seeking to gain a majority on the national governing board in elections scheduled for Sept. 18.

The emergence of a serious challenge to SAG's ruling coalition, a Hollywood-based group of moderates known as Membership First, likely means that the 3 1/2-week-old standoff between the union and studios will drag on for at least two more months.

Candidates running on the Unite for Strength slate include two stars from TV's "Grey's Anatomy" spinoff "Private Practice" -- Kate Walsh and Amy Brenneman -- as well as Doug Savant from "Desperate Housewives" and "Chicago Hope" veteran Adam Arkin.

They accuse the current leadership of mishandling labor talks and straining relations with SAG's smaller sister union, the American Federation of Television and Radio Artists, through SAG's failed campaign to scuttle a contract negotiated separately between AFTRA and the studios.

The Membership First coalition, led by SAG President Alan Rosenberg, the husband of "CSI" star Marg Helgenberger, holds a slight majority on the board. It was swept to power in 2005 after pledging to get tougher with the studios in contract negotiations.

But opponents say Rosenberg's confrontational stance toward AFTRA has backfired by allowing the studios to play one union off the other.

UNION INFIGHTING

"As our current predicament makes clear, actors lose out when we face off as separate warring camps against the media conglomerates in contract negotiations," Arkin said in a statement. "I'm concerned for future negotiations if we don't change the leadership that has brought us to this point."

SAG representatives had no immediate comment. But Rosenberg was quoted by the Los Angeles Times on Thursday as saying his critics are misguided.

"The future of SAG and the ability of actors hangs in the balance here, and it's AFTRA that has put us all in jeopardy," he said.

It was an apparent reference to AFTRA's decision earlier this year to break off the two unions' 27-year joint bargaining pact and go it alone in contract negotiations.

Rosenberg has said AFTRA's resulting TV-only deal with studios fell short in several respects, including payments for actors in new media, undermining SAG's ability to secure a better terms under its larger contract for TV and movies.

The old SAG contract, covering 120,000 performers, expired hours after the studios presented the union with their "final" offer as a take-it-or-leave-it proposition on June 30.

The terms essentially mirror those in the AFTRA deal, and in contracts negotiated with Hollywood writers and directors.

SAG presented a counteroffer on July 10, but the studios refused to budge, insisting they were through negotiating and that their proposal be put to union members for a vote.

SAG leaders have so far been unwilling to do so, or to seek the authorization of members to call a strike.

Many industry watchers doubt SAG could muster the 75 percent majority needed to back a walkout, in part due to lingering fatigue from a 14-week writers strike that ended in February.

In the meantime, actors continue to work under terms of the old contract.

Neither side is likely to take decisive action to break the stalemate before the elections, said entertainment attorney Jonathan Handel, a former co-counsel for the Writers Guild of America with ties to labor and management.

"There's not a chance there will be a deal before Sept. 18," he said. "And what happens then depends on the results of the election."