The union and employers negotiating a new labor contract for more than 22,000 U.S. West Coast port workers said high-stakes talks that are being closely watched by industry and the White House would continue after the agreement expired late on Friday.

The agreement covers 29 Pacific Coast ports stretching from California to Washington State that handle almost 40% of U.S. imports. Any work slowdowns or stoppages could roil the nation’s already battered supply chains, stoke inflation, and exacerbate pressure on a weakening economy that is sinking President Joe Biden’s approval ratings.