(Adds activity at other refineries, details, background)
HOUSTON, March 13 (Reuters) - A strike by the UnitedSteelworkers (USW) local union at the Marathon Petroleum Corp Galveston Bay Refinery in Texas City, Texas, willcontinue as long as the company refuses to accept the terms of anewly-negotiated national agreement without encumberances, saida union official on Friday.
The national agreement, often referred to as "the patternagreement," reached on Thursday by officials from the union andlead refinery owner negotiator Shell Oil Co is supposed to beoffered by the companies at all refineries and chemical plantsrepresented by the USW.
"The company refuses to offer the pattern unencumbered,"said W.E. Sanders, sub-director for USW District 13, whichcovers Arkansas, Louisiana, Oklahoma and Texas. "The companyclearly knows its obligations under the pattern."
A Marathon representative was not immediately available todiscuss the dispute.
Marathon is the only company so far said to be unwilling tooffer the national agreement at one of its locations. Sixcompanies own the 15 plants where 6,550 USW members remain onstrike pending formal ratification of the national and localagreements, which will include the terms of return-to-workplans.
Striking workers are expected to return to their jobs withintwo weeks.
Workers at Marathon's Catlettsburg, Kentucky, refinery wereexpected to remain off of their jobs while the company and theUSW discuss local issues, according to a report from theHuntington, West Virginia, Herald-Dispatch.
Shell, which is the U.S. arm of Royal Dutch Shell Plc, and the USW were negotiating on Friday areturn-to-work agreement framework that will be used by thelocal unions.
The strike by the USW began on Feb. 1 and spread to 15plants, including 12 refineries that account for one-fifth ofU.S. capacity. It is the largest national work stoppage byrefinery workers since 1980.
Workers at the Shell refinery and chemical plant in DeerPark, Texas, and three Motiva Enterprises refineries,of which Shell is a co-owner, were awaiting the return-to-workframework agreement, expected by Saturday.
Negotiations were continuing between the USW local union andLyondell Basell Industries over local issues at thecompany's Houston Refinery, said a source familiar with thetalks. A federal mediator has joined the talks.
A federal mediator may also join the talks between MarathonGalveston Bay workers and the company when they restart, Sanderssaid. (Reporting by Erwin Seba; Editing by Diane Craft, Bernard Orr)
