Shortly after talks between union and oil company representatives ended on Friday night, the union notified Motiva Enterprises [MOTIV.UL] of a strike by its members at the company's 600,250 barrel per day (bpd) refinery in Port Arthur, Texas.

The USW is also giving notices of strikes to begin in 24 hours at Motiva's refineries in Convent and Norco, Louisiana, and the Shell Oil Co. chemical plant in Norco, the union said.

"The industry’s refusal to meaningfully address safety issues through good faith bargaining gave us no other option but to expand our work stoppage," USW International President Leo Gerard said in a statement.

Motiva is a 50-50 joint venture of Royal Dutch Shell Plc and Saudi Aramco [SDABO.UL]. Shell's U.S. arm Shell Oil Co is the lead oil company negotiator in talks with the USW for a national agreement on safety, pay and benefits.

More than 5,000 workers at 11 plants, including nine refineries accounting for 13 percent of U.S. production capacity, are walking picket lines in the largest national refinery strike since 1980.

This is the first expansion of the strike since Feb. 6, when workers at BP Plc-operated (BP.L) refineries in Indiana and Ohio were told to begin a work stoppage the following day.

(Reporting by Erwin Seba; Editing by Nick Macfie and Clarence Fernandez)