The Pacific Maritime Association has accused dockworkers at both the Long Beach and Los Angeles ports of taking “unit breaks,” in order to slow productivity in an effort to gain leverage in contract negotiations.

The PMA said change in breaks could possibly slow work at the ports by as much as 15 percent. Workers with the Longshore and Warehouse Union typically stagger their breaks so work continues seamlessly throughout the day. The workers get two “coffee breaks” per day, in the morning and afternoons.

“While it is not yet clear what impact, if any, this move will have on productivity, it is concerning that the union has taken this step unilaterally during such a sensitive time in the contract negotiations,” the PMA said, admitting that despite the group breaks on Friday, productivity “appeared normal.”

However, Steve Getzug, a spokesman for the PMA, said the coordinated breaks were continuing Monday and added that productivity was in fact being limited by as much as 10 to 15 percent.

“This is something we’re going to have to watch,” he said.

The disruption follows the July 1 expiration of the six-year contract between the union and port employers, with the union refusing an employer request for a temporary extension of the previous contract but said it would keep the ports working normally.

The ILWU had not commented on the PMA claims but has consistently said that it wants to keep the ports operating normally during negotiations.

The union employed so-called “slow-down tactics” during the previous contract’s negotiation period which was in 2002. The “slow-down tactics” resulted in a 10-day lockout of workers by employers costing the U.S. economy $1.5 billion, according to the PMA.

The ports of Long Beach and Los Angeles handle more than 40 percent of all containerized goods that are imported into the U.S. The PMA and ILWU reached a tentative agreement on healthcare and pensions on June 17, but the toughest issue in the negotiations is likely to be the introduction of new, labor-saving technology at the coast’s relatively antiquated ports which the union fears will cost jobs