LOS ANGELES - Striking workers shut down the largest terminal at the Port of Los Angeles for the second day Wednesday, and the job action later widened to close three terminals at the Port of Long Beach, threatening to paralyze the nation's busiest port complex.

About 70 clerical workers struck the APM Terminals operations on Pier 400 at Port of Los Angeles on Tuesday, raising the ante in a 2 1/2-year-old contract battle over union claims that management has been outsourcing well-paid jobs out of state and overseas.

Only a handful of workers were picketing early Wednesday, but dockworkers were honoring the walkout and the terminal remained closed, although only two cargo ships were affected, port spokesman Phillip Sanfield said.

"It's not crippling the port by any means. We've got eight other container terminals up and running," he said.

The port is not operating at its peak because shipment of Christmas goods ended several weeks ago.

"The holiday goods are either already in the stores or in warehouses," Sanfield said.

Port of Long Beach officials said Wednesday afternoon that a labor action there had shut down operations at three of six container terminals.

About a quarter of a billion dollars in goods travel through the three terminals every day, Long Beach port spokesman Art Wong said.

Like Los Angeles, Wong said the Long Beach port's longshoremen were honoring the clerical workers' strike and didn't cross picket lines.

Los Angeles and Long Beach together have the nation's busiest port complex. The twin harbors handled $273 billion worth of cargo last year.

The strikers are from the Office Clerical Unit of the International Longshore and Warehouse Union's Local 63. Their contracts with 14 companies that operate most of the terminals at the twin ports expired in June 2010.

Years of contract-renewal negotiations ended with talks breaking off on Monday, leading to the walkout.

An arbitrator ruled Tuesday night that the union was negotiating in bad faith with shippers and the strike was invalid. But the order was ignored pending a planned Wednesday meeting between the union and shippers.

A second arbitrator also was expected to rule within two days on whether to uphold that order.