Truck drivers who haul goods from the nation's busiest port complex in Southern California could stay off the job next week as part of a long-running labor dispute, union officials said Friday.

It won't be clear until next week how many of the drivers stay away, but the action could disrupt business at the ports of Long Beach and Los Angeles as soon as Monday, after an expected vote this weekend.

About 16,000 drivers work at the ports, most of them independent contractors for trucking companies. The truckers say they face shrinking wages and want to become employees of the trucking companies, which they say would mean better wages and workplace protections.

Port of Los Angeles spokeswoman Rachel Campbell said it was too soon to say what, if any, impact a work stoppage could have on port business. Port of Long Beach spokesman Art Wong said "we are hoping we can continue to move cargo and people can go about their business."

Earlier this year, tough contract negotiations with dockworkers nearly closed 29 seaports from San Diego to Seattle, causing major delays in the delivery of billions of dollars of imports and exports.

Teamsters spokeswoman Barb Maynard said the drivers have been victims of "persistent wage theft that has characterized the industry and impoverished so many drivers."

Last summer, strikes by truckers briefly closed the massive ports.

Trucking companies have argued that driver pay is good and picketing at the ports did not represent the majority of drivers.

They object especially to the timing of the unrest as the port is still recovering from a major labor stoppage by dockworkers.

"We are not surprised that the Teamsters are looking to picket," said Weston LaBar, executive director of the Harbor Trucking Association, in a statement. "What I am surprised of is the timing of it. The ports are working diligently to dig out from the backlog due to congestion, which was compounded by labor issues. I believe now is a horrible time to introduce any slow-downs to the supply chain."

The Southern California ports are the primary West Coast gateway for hundreds of billions of dollars of annual trade with Asia.