(Adds additional strike notices, USW statement)
HOUSTON, Feb 20 (Reuters) - The U.S. refinery strike waswidening on Friday night as workers at the nation's largestrefinery gave notice of a walkout beginning at 12 a.m. (0600GMT) on Saturday, the United Steelworkers union (USW) said.
Shortly after talks between union and oil companyrepresentatives ended on Friday night, the union notified MotivaEnterprises of a strike by its members at thecompany's 600,250 barrel per day (bpd) refinery in Port Arthur,Texas.
The USW is also giving notices of strikes to begin in 24hours 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 safetyissues through good faith bargaining gave us no other option butto expand our work stoppage," USW International President LeoGerard said in a statement.
Motiva is a 50-50 joint venture of Royal Dutch Shell Plc and Saudi Aramco. Shell's U.S. arm Shell OilCo is the lead oil company negotiator in talks with the USW fora national agreement on safety, pay and benefits.
More than 5,000 workers at 11 plants, including ninerefineries accounting for 13 percent of U.S. productioncapacity, are walking picket lines in the largest nationalrefinery strike since 1980.
This is the first expansion of the strike since Feb. 6, whenworkers at BP Plc-operated (BP.L) refieneries in Indiana andOhio were told to begin a work stoppage the following day. (Reporting by Erwin Seba; Editing by Nick Macfie and ClarenceFernandez)