The United Steelworkers union told its workers at nine U.S. refineries and chemical plants to strike early Sunday morning, though both sides have said they still hope to reach an agreement over pay, benefits and safety.

Negotiations between U.S. refiners and the union failed to reach a deal by a 12:01 a.m. Sunday deadline. USW workers have been instructed to finish their shifts and then leave nine refineries from Houston, Texas to the Los Angeles, Calif.

The union has been trying to negotiate a new three-year agreement that addresses industrywide wage increases, safety conditions and staffing issues. The deal would form the baseline for additional talks between companies and local unions, and cover 30,000 workers at 230 refineries, oil terminals, pipelines, and petrochemical plants.

USW represents workers at 65 fuel-making plants around the U.S. which it says account for nearly two-thirds of the country’s refining capacity.

USW said the plants where workers will strike include: LyondellBasell Industries ’ plant in Houston, Texas; Royal Dutch Shell PLC’s complex in Deer Park, Texas; Marathon Petroleum Corp. ’s sites in Galveston, Texas City and Catlettsburg, Ky; and three Tesoro facilities in Washington and southern California.