LOS ANGELES (AP) — West Coast shippers accused dockworkers at the nation’s largest port complex of intentionally slowing cargo shipments for the sixth day Wednesday as the two sides negotiate a new contract.

The workers have been taking breaks at the same time every day since Friday and have been working slower, said Steve Getzug, a spokesman for Pacific Maritime Association.

He said the coordinated breaks, which deviate from the usual staggered breaks, have halted operations for 15 to 30 minutes. Other job actions include tractor drivers moving unusually slow and brief delays during the transferring of containers onto trucks or to and from ships, he said.

“What we’re talking about here is fewer containers being moved hour to hour, which has a cumulative impact,” Getzug said. “The kinds of actions we’re seeing are of concern to us because it has obviously an impact on operations, but it also signals that the union is going back to tactics that they used in the past to influence negotiations when a contract runs out.”

International Longshore and Warehouse Union spokesman Craig Merrilees said the shippers were “exaggerating” and that both sides were still talking.

About 26,000 workers at 29 ports in California, Oregon and Washington have been working without a contract since July 1, making it impossible for shippers to contest what they believe to be disruptive tactics.

On Friday, workers at the Tacoma, Wash., port walked off the job for four hours, leaving 82 containers on the dock instead of on a departing ship, Getzug said.

Merrilees said the protest was triggered by a dispute during negotiations for a local contract. Workers stopped working after a local PMA representative walked away from the bargaining table. The issue was quickly resolved and both sides resumed negotiations the next day, he said.

The twin ports of Los Angeles and Long Beach handle about 40 percent of the nation’s cargo.

The union and the shippers are seeking to avoid a repeat of a bitter labor dispute that led to a 10-day lockout in 2002 and caused an estimated $15 billion in economic losses.

Both sides have already reached a tentative agreement on health care benefits. Wage, pension, safety and productivity issues remain under discussion.