WASHINGTON (AP) — The United Food and Commercial Workers union is rejoining the AFL-CIO, giving the labor federation more power and resources to help revitalize the struggling union movement.

The move comes eight years after UFCW and six other unions left the AFL-CIO in a bitter dispute that reduced the federation's clout and took away millions in dues from its budget. The breakaway unions formed a rival federation called Change to Win after complaining the AFL-CIO wasn't doing enough to halt steep membership declines.

UFCW President Joe Hansen said Thursday that greater labor unity is needed to fend off efforts to weaken union membership and influence.

"It is about joining forces to build a more united labor movement that can fight back against the corporate and political onslaught facing our members each and every day," Hansen said.

UFCW has 1.3 million members who work in the retail, meat packing and food processing industries. It will become the AFL-CIO's largest private sector union, giving the federation about 13.3 million members.

Two other unions that left the AFL-CIO in 2005 have also come back in recent years, including the Laborers and the union of hotel, restaurant and clothing workers known as UNITE HERE.

The announcement Thursday comes as AFL-CIO President Richard Trumka is pushing for major changes that could see the federation expand to include environmental and civil rights groups like the Sierra Club and the NAACP. Trumka says organized labor needs to broaden its reach to workers beyond those with collective bargaining agreements.

The move by UFCW leaves just three unions remaining in Change to Win — the Service Employees International Union, the Teamsters, and the United Farm Workers. While Change to Win has been more aggressive in helping its unions wage new organizing campaigns, it never emerged as a true rival to the AFL-CIO, which has been the face of organized labor for more than a half century. Former SEIU leader Andy Stern — who spearheaded the 2005 split — left the union in 2010 and is no longer a force in organized labor.

Despite the split, unions in the two federations have worked together and pooled resources to fight efforts in Wisconsin, Ohio and other states where officials have sought to take away collective bargaining for public employees and to curb other union rights.