US west coast ports operating at full speed after tentative labour deal reach

US west coast ports have begun resuming full operations after a tentative labour deal was reached between a group of shipping companies and a powerful dockworkers union after nine months of negotiations, settling a dispute that disrupted the flow of cargo through 29 ports and snarled trans-Pacific maritime trade with Asia.

But Gene Seroka, the executive director of the Port of Los Angeles, the nation's largest, said on Saturday it would take three months "to get back a sense of normalcy".

The volume of cargo that west coast dockworkers and their employers must clear, now that they've reached a tentative contract agreement on Friday evening, is staggering. Put in a line, the containers would stretch 930km. Stacked up, they'd rise nearly 400km - about the orbiting altitude of the International Space Station.

The agreement, confirmed late on Friday in a joint statement by the two sides, was reached three days after Thomas Perez, the US labour secretary arrived in San Francisco to broker a deal with the help of a federal mediator who had joined the talks six weeks earlier.

The White House called the deal "a huge relief" for the economy, businesses and workers. President Barack Obama urged "the parties to work together to clear out the backlogs and congestion in the west coast ports as they finalise [the] agreement", the White House said.

The 20,000 dockworkers covered by the tentative five-year labour accord have been without a contract since July.

The dispute had reverberated throughout the US economy, extending to agriculture, manufacturing, retail and transportation. Supply chain disruptions were hit from automakers to consumers of French-fried potatoes at McDonald's restaurants in Japan.