The United Auto Workers is the latest union to join the BlueGreen Alliance, which unites labor and environmental groups pushing for greenhouse gas limits and other policies to create "green" jobs.
The UAW - also known as the International Union, United Automobile, Aerospace and Agricultural Implement Workers of America - claims to have more than 390,000 active members.
"UAW members produce best-in-class cars and trucks, key vehicle components, and top quality heavy-duty trucks, and we know that we can rebuild the American auto industry by building cleaner, more efficient vehicles - and developing the technologies that will get us there," UAW President Bob King said in a statement Monday about joining the BlueGreen Alliance.
"We have enormous opportunities to revitalize this industry, and the American economy, by embracing the clean energy economy of the future," he said.
The BlueGreen Alliance was formally launched in 2006, and grew out of a less formal collaboration between the Sierra Club and the United Steelworkers.
It also includes the Service Employees International Union, the Natural Resources Defense Council, the Communications Workers of America and several other unions.
The BlueGreen Alliance is in the midst of a cross-country bus tour aimed at reviving a broad Senate energy and climate-change bill that's currently on ice on Capitol Hill.