Former Sen. John Edwards will start his Labor Day in Pittsburgh to accept a presidential endorsement from the United Steelworkers.

Mr. Edwards is expected to appear with United Steelworkers president Leo Gerard at a 9 a.m. rally at the Mellon Arena, the kickoff site for the city's annual Labor Day Parade. The former North Carolina senator will not stay for the parade, heading off immediately after the rally to another Labor Day event in Iowa.

Neither the USW nor the Edwards campaign would comment on the planned endorsement. It comes as the labor movement begins to head in different directions in the 2008 nomination fight.

On Wednesday, the International Union of Firefighters threw its support to Sen. Chris Dodd, D-Conn. Today, the International Association of Machinists and Aerospace Workers endorsed Sen. Hillary Rodham Clinton, D-N.Y., and Republican Mike Huckabee in their respective presidential primaries, while Mr. Edwards picked up the backing of the United Brotherhood of Carpenters and Joiners of America.