West Coast terminal operators said that they will shut down the nation's largest port complex Friday if longshoremen don't end a work slowdown against a stevedore there.

Employers at the Port of Los Angeles-Long Beach will lock out dockworkers at 8 a.m. local time if the International Longshore and Warehouse Union fails to provide enough labor to a Stevedoring Services of America terminal.

The lock-out will be confined to Southern California.

The threat by the Pacific Maritime Association is significant because, in the past, the greatest fear of shipping lines and terminal operators was that the powerful ILWU would strike during contract negotiations. An employer lock-out was considered out of the question.

The new stance by employers indicates a determination by shipping lines and terminal operators to prevent union work slowdowns and to negotiate a contract that results in greater productivity at West Coast ports.

Thursday's announcement follows four days of slowdowns against SSA, which has terminal operations at all major West Coast ports. The union accused SSA of standing in the way of a successful conclusion to contract negotiations, and of union-busting tactics.

The ILWU is engaged in a bitter jurisdictional dispute with the International Association of Machinists over control of maintenance and repair jobs at an SSA terminal in Long Beach. Some employers say the union's main objective is to force SSA to assign those jobs to the ILWU.

PMA President Joseph Miniace said the ILWU is blatantly denying skilled labor to SSA in Long Beach. SSA on Thursday requested 31 longshoremen to operate critical container-handling machines known as top-handlers and transtainers; the union supplied only three skilled operators.

The ILWU continues to supply sufficient manpower to the other terminals in Los Angeles-Long Beach, so its claim that there is a shortage of manpower during the peak shipping season is not true, Miniace said.

Union officials were not immediately available for comment.

A China Ocean Shipping Co. vessel has been delayed at SSA's Pacific Container Terminal as a result of the slowdown, and trucks are backed up at the terminal gate, Miniace said.

The joint ILWU-PMA coast arbitrator Sam Kagel offered to mediate the dispute, but the ILWU turned down his request, Miniace said. Kagel has been the coast arbitrator for more than 40 years.

The PMA is encouraging terminal operators in Northern California and the Pacific Northwest to remain open. Los Angeles-Long Beach accounts for about 69 percent of the containerized cargo moving through the West Coast.

By Bill Mongelluzzo