The United Steelworkers union said more than 14,000 members covered by a contract with ArcelorMittal have authorized a strike against the world's largest steel producer if a new labor agreement cannot be negotiated.

The contract expires Monday. Talks have been going on since April. USW members who work for U.S. Steel are voting on a proposed four-year labor agreement after the company and union announced tentative agreement Aug. 12. The contract would replace one that also expires Monday. It covers about 16,000 workers at U.S. Steel's domestic sheet mills, including about 2,600 at its Edgar Thomson plant in Braddock, the Irvin plant in West Mifflin and the Clairton coke plant.