For a fourth day, dockworkers at West Coast ports in the United States are disrupting international trade, according to the Pacific Maritime Association.

Two of the six marine terminals at the Port of Long Beach remained closed during the day shift Monday, as "operators of those terminals made the decision to close based on operational needs, and will reopen for the evening shift," the port said in a statement.

The association (PMA) and International Longshoremen and Warehouse Union represents the dockworkers who have been negotiating a new contract since May 10, 2022. The union, which represents 22,000 workers at 29 US West Coast ports, said on Friday that they remained committed to negotiating a good agreement for their workers as talks continued. The union did not address the work disruptions.

The PMA says union leaders have been implementing disruption tactics since Friday — slowing operations at West Coast ports and forcing the ports to close shipping terminals.

"Over the weekend and continuing today, the ILWU has continued to stage concerted and disruptive work actions that have slowed operations at key marine terminals at the Ports of Los Angeles and Long Beach and elsewhere on the West Coast, including the Ports of Oakland and Seattle," the PMA said in a statement Monday.

The Port of Los Angeles said one terminal, Fenix Marine, closed its gates during the lunch hour for the day on Monday, but a spokesperson could not provide details on why.

The Port of Oakland reported earlier this morning that all terminals were open and operational. The terminal operators at the Ports of Seattle and Tacoma did not return CNN's requests for comments.

The West Coast ports, which once handled the bulk of US trade — especially during the pandemic, have relinquished some volume to the Gulf and East Coast Ports. Shippers started to worry about whether the West Coast ports could handle high volume cargo given the mess that ensued off the coast of California during the pandemic as ships and US goods were stuck at sea for weeks on end. The West Coast ports have said they are capable and open for business.

"The ILWU's coast-wide work actions since June 2 are forcing retailers, manufacturers and other shippers to ship cargo away from the West Coast in favor of ports on the Atlantic and Gulf coasts. Much of the diverted cargo may never return to the West Coast," the PMA said.

Amid news of disruptions, the National Retail Administration is calling on the Biden administration to intervene in negotiations to resolve the labor dispute ahead of the summer, heading into the peak holiday shipping season.

"Thousands of retailers and other businesses depend on smooth and efficient operations at the ports to deliver goods to consumers every day," said David French, senior vice president of government relations at the National Retail Federation. "It is imperative that the parties return to the negotiating table. We urge the administration to mediate to ensure the parties quickly finalize a new contract without additional disruptions."

The ILWU says negotiations will continue as the two sides approach one year since their contract expired on July 1, 2022.

"Any reports that negotiations have broken down are false," said Willie Adams, president of the ILWU, on Friday. "We are getting there but it's important to understand that West Coast dockworkers kept the economy going during the pandemic and lost their lives doing so. We aren't going to settle for an economic package that doesn't recognize the heroic efforts and personal sacrifices of the ILWU workforce that lifted the shipping industry to record profits."