The agreement is still subject to a ratification vote by nearly 14,000 workers at 15 of the company's U.S. locations, the USW said in a release posted on its Web site.
Details of the agreement were not disclosed.
"After 10 long weeks of difficult negotiations that continued past the expiration of our previous contract, the hard work of our committee has resulted in a tentative agreement with ArcelorMittal," USW International President Leo W. Gerard said. "Our members' unwavering solidarity throughout the bargaining process in the face of management's high-risk scare tactics and demands for major cutbacks has been rewarded."
USW District 1 Director David McCall, who led the union's bargaining team, said ArcelorMittal management had "nearly destroyed" the relationship between the company and union with its demands.
"We are proud that we preserved our wages, benefits and contractual protections for seniority as well as maintaining the limits of work done by outside contractors," McCall said.