After a weekend shutdown, ports on the West Coast were back in business on Tuesday.

The White House dispatched U.S. Labor Secretary Tom Perez to San Francisco to try to broker a deal between  dockworkers and shipping companies. They’ve been locked in a contract dispute that for months has slowed the flow of cargo and caused ripples throughout the global economy.

But, even when a deal is reached, port officials say it could take weeks to clear the backlog.