LOS ANGELES (AP) — Companies that handle billions of dollars of cargo at West Coast seaports said Friday they will hire far fewer workers this weekend, the latest escalation in a contract dispute with dockworkers that threatens to shut down a vital link in U.S.-Asia trade.

The association representing port terminal operators announced its members would not hire crane drivers to move containers on and off massive ocean-going ships. Instead, employers could order smaller crews to clear already-unloaded containers from congested dockside yards.

The announcement could foreshadow a full port shutdown as soon as Monday, or it could be a hardball bargaining tactic designed to force a contract after nine months of talks.

Congestion has been a huge issue at the West Coast’s 29 ports, where containers are taking two to three times longer than usual to clear dockside yards on their way to distribution warehouses.

The International Longshore and Warehouse Union has blamed employers, saying they failed to manage the supply chain efficiently.

 The Pacific Maritime Association, which represents shipping companies as well as port terminal operators, has said for months that workers have slowed their work by about 50 percent to gain bargaining leverage.

Last month, employers cut crane crews at night, saying the focus needed to be on decongesting dockside yards.

“After three months of union slowdowns, it makes no sense to pay extra for less work,” maritime association spokesman Wade Gates said of weekend work in a written statement.

Earlier this week, the maritime association said that as early as Monday, ports could become so gridlocked with containers there’s no place to put cargo unloaded from incoming ships. The association’s CEO said that “meltdown” point would result in a worker lockout that would shutter ports that handle about one-quarter of the nation’s international trade — about $1 trillion in commerce annually.

Employers made what CEO James McKenna called their “best offer” Tuesday, which included wage increases of about 3 percent annually, an increase in pension contributions and the maintenance of health benefits.

The union responded to his lockout warning by saying that while a contract deal was close, it would not be bullied.

As contract negotiators for the association and dockworkers’ union met Friday in San Francisco, the shift cutting provoked a harsh response.

“Closing down the ports over the weekend is a crazy way to treat customers that only adds to the industry-caused congestion and delays,” union spokesman Craig Merrilees said.

Exporters, including farmers and cattle ranchers, say their goods are stalled on the docks — while importers of electronics, textiles, furniture, car parts and a range of other goods made in Asia also are affected by port congestion.

In response to Friday’s development, an association representing retailers admonished both sides.

“Temporarily suspending port operations is just another example of the International Longshore and Warehouse Union and Pacific Maritime Association shooting themselves in the collective bargaining foot,” Jonathan Gold, vice president for supply chain at the National Retail Federation, said in a statement. “Enough is enough.”