The powerful Steelworkers union is endorsing Barack Obama for president.

The endorsement should help Obama attract some of the blue-collar workers that his campaign has been seeking during the primary against presidential rival Hillary Rodham Clinton.

The Steelworkers endorsed one day after former Democratic candidate John Edwards backed Obama. The Steelworkers had endorsed Edwards before he dropped out of the presidential race.

Both Obama and Clinton had strongly courted the Steelworkers, whose headquarters are in Pittsburgh. The union has about 600,000 active members in the U.S.