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.