The impact on the movement of cargo around the sprawling port complex, the main gateway for hundreds of billions of dollars of trade with Asia, was limited. But the threat of a broader disruption loomed if striking truckers take their pickets from offices of their employers to the dockside terminals where cranes load and unload containers massive oceangoing ships.

The truckers say the companies have prevented them from unionizing and improperly classified them as contractors — rather than full-time employees — to minimize wages and benefits. They say that their paychecks often amount to below minimum wage once the cost of renting and maintaining a truck is factored in, and have filed lawsuits and complaints with state and federal labor agencies to change their status. Companies counter that pay is good and those picketing do not represent the majority of drivers.