Sunoco Inc. (SUN) and the United Steelworkers reached a tentative deal on a contract for workers at the Philadelphia refinery, the union said Monday night.

The old contract has been extended for 24 hours so that both sides can review the new contract language on Tuesday before signing, union spokeswoman Lynn Baker said in a news release.

The workers were threatening to strike over this past weekend. The two sides were disagreeing over potential layoffs.

-By Susan Daker, Dow Jones Newswires; 713-547-9208; susan.daker@dowjones.com