* Grain shipper accuses union of slowing operations
* Company has clashed with workers over contract terms
* Workers say Columbia Grain never wanted an agreement
* Protesters gather outside export terminal
By Teresa Carson
PORTLAND, Oregon, May 4 (Reuters) - Grain shipper Columbia Grain on Saturday locked out longshore workers in the U.S. Pacific Northwest in the latest escalation of a simmering labor dispute.
The company, owned by Japanese trader Marubeni Corp , said it took action because members of the International Longshore and Warehouse Union (ILWU) were purposefully slowing operations at its terminal at the Port of Portland, a key outlet for exports to Asia.
Columbia Grain said it had contingency plans to keep operations running during the lockout.
At least 50 workers gathered in front of the terminal gates on Saturday afternoon in a peaceful protest against the lockout. Some carried blue and yellow picket signs that blasted Columbia Grain as "UNFAIR."
The protesters set up canopies for shade during an unseasonably warm day and were distributing supplies of bottled water, snacks and fried chicken.
"We've been locked out," Bruce Holte, president of ILWU Local 8, told Reuters at the protest.
A contract between the union and the Pacific Northwest Grain Handlers Association, a collective negotiating group that includes Columbia Grain, United Grain Corp, Louis Dreyfus and TEMCO, expired in September.
The two sides were unable to come to a contract agreement so terminal operators declared an impasse late last year, and imposed the terms of their final contract offer.
TEMCO, a joint venture of U.S. agribusinesses Cargill Inc and CHS Inc, said in February that it reached a tentative agreement with the ILWU on its own. ILWU-represented employees at the Columbia Grain facility and the two Dreyfus elevators continued to work under the company's final contract offer terms.
Columbia Grain said on Saturday that bargaining has stalled.
Longshore workers are "engaging in 'inside game' tactics, including slowdowns, work-to-rule, and demands for repeated inspections of the same equipment - all designed to negatively impact Columbia Grain's operations," according to the company.
The region's nine export terminals are a critical outlet for U.S. grain exports. Nearly half of U.S. wheat exports and about a quarter of all U.S. grain and oilseed exports leave the country via the Pacific Northwest.
Columbia Grain has 42.5 million bushels of storage capacity and exports nearly 160 million bushels of wheat, barley, corn and soybeans through a state-of-the-art grain elevator at Terminal 5 in Portland, according to owner Marubeni.
The union on Saturday said Columbia Grain never wanted to reach an agreement with the longshore workers and had hired replacement workers last fall while negotiations were still in their early stages.
"Marubeni is hurting the Northwest's economy by putting local union workers out on the street instead of allowing us to go to work," Holte said in a statement.
The union in March filed an unfair labor practice charge against United Grain Corp, a unit of Japanese trading company Mitsui & Co, after its members were locked out of the company's Vancouver, Washington, grain export terminal.