The U.S. Chamber of Commerce is calling on President Joe Biden to intervene in a labor dispute involving U.S. West Coast ports that has seen container ships face delays as work disruptions escalate.

“We urge you to appoint an independent mediator to help the parties reach a voluntary agreement,” Chamber president and chief executive officer Suzanne Clark wrote in a letter to the president June 9 as talks between port employers and dockworkers approach a one-year mark without a contract.

“This step is necessary to avoid potentially billions of dollars in economic damage to the American economy before it occurs,” Clark added. “We urge your Administration to continue engaging directly with both parties and to consider additional steps that may be necessary in the event of a widespread work stoppage.”

Labor shortages at West Coast ports that began June 2 stretched into the week, making it the longest disruption related to contract talks since the White House intervened in 2015. A previous labor contract covering 22,000 dockworkers at 29 ports expired on July 1, 2022.

Read more: Union Workers Halt Operations at Several West Coast U.S. Ports

The situation appeared to improve June 8, though dozens of container ships scheduled during the week of June 16 for the twin ports of Los Angeles and Long Beach were affected by delays of a day or two, according to the Marine Exchange of Southern California.

There are concerns the delays can have broader fallout. Ships that are off-schedule can cause disruptions at other ports on their routes.

Clark warned of a crippling effect on the US economy.

“A serious work stoppage at the ports of Los Angeles and Long Beach would likely cost the U.S. economy nearly half a billion dollars a day – and a more widespread strike along the West Coast could cost approximately $1 billion per day,” Clark said in the letter.

The White House said during the week of June 9 that Biden respects the collective bargaining process and wants negotiations between port employers and workers to continue.