SAG’s officially mended fences with AFTRA, two years after a messy breakup.

The national board of the Screen Actors Guild voted Saturday to resume the guild’s negotiating partnership with the American Federation of Television & Radio Artists. On Oct. 1, SAG and AFTRA will begin seven weeks of talks with the Alliance of Motion Picture & Television Producers over the primetime-feature master contract.

The vote received 78% support in the board’s videoconference meeting — two weeks after AFTRA’s national board unanimously approved joint negotiations.

Next steps for the performers’ unions will be to appoint members to the “wages and working conditions” committee that will conduct a series of meetings to start hammering out details of the contract proposal.

“Bargaining together is a smart decision, and voting up this agreement clearly serves the best interests of all SAG members,” said SAG president Ken Howard.

SAG has about 120,000 members, AFTRA has some 70,000, with about 45,000 thesps holding dual membership.

Both the SAG and AFTRA deals expire June 30, 2011. A spokesman for the AMPTP had no comment Saturday.

The joint bargaining pact amounts to a milestone in the efforts of SAG’s leaders to patch up relations with AFTRA, two years after AFTRA angrily spurned SAG and negotiated its own primetime deal.

The relationship turned ugly in 2007 and 2008, with the two unions sniping at each other over jurisdiction and tactics. The self-styled progressives of SAG’s Membership First faction, led by then-president Alan Rosenberg, repeatedly blasted AFTRA over its willingness to compromise with the AMPTP.

But Membership First began to lose support in two subsequent elections as SAG members backed a coalition of moderates who pledged to improve relations with AFTRA. The AFL-CIO brokered a “non-raiding, non-disparagement” agreement for last year’s commercial contract negotiations so that the two unions could negotiate jointly; that pact will remain in effect for the upcoming talks.

The joint bargaining takes place under terms of the three-decades-old Phase One agreement between SAG and AFTRA — which gives the unions 50-50 representation at the bargaining table. That 50-50 arrangement is a sore spot for the Membership First faction, which has long contended that SAG should have more seats to reflect the guild’s dominance of work under the feature-primetime contract.

But SAG’s dominance in primetime has eroded significantly in the past two years because the two unions have shared jurisdiction in TV shows that are shot in digital formats — and producers of nearly all the new shows have opted for AFTRA deals during that time, even though SAG’s leadership has moved away from confrontation with the companies.

Membership First partisans have complained in recent weeks that SAG staff and leaders are not doing enough to sign up new shows, with about two dozen picketers protesting outside Saturday’s meeting.

SAG First VP Anne-Marie Johnson, in a recent letter to members, said that the trend could mean that “thousands” of SAG members will no longer be eligible for the union’s health coverage or pension credit points.

SAG hasn’t responded officially to those complaints. The Unite for Stength coalition has asserted that the employers’ move toward AFTRA shows the need for both unions to merge, as a single union would be more powerful at the bargaining table, end double dues and stop the destructive splitting of pension and health contributions.

At Saturday’s meeting, Membership First reps opposed the joint bargaining due to constraints in the “non-raiding, non-disparagement” agreement — asserting that it precludes board members from publicly opposing AFTRA strategies.

Justine Bateman, who had called AFTRA a “scumbag” union, resigned from the national board last summer because of those concerns.

SAG — and now AFTRA — are the only Hollywood unions with a negotiations date already set. The master feature-primetime contract for the DGA also expires June 30, 2011. The Writers Guild of America’s deal — hammered out in early 2008 after the 100-day strike — expires May 1, 2011.