Nearly 50,000 members of the International Longshoremen’s Association (ILA) are on strike Tuesday against the nation’s East and Gulf Coast ports, choking off the flow of many of the nation’s imports and exports in what could become America’s most disruptive work stoppage in decades.

The strike is disrupting ports that handle more than half of U.S. trade in shipping containers, with the economic bite growing worse if the standoff drags on.

Thousands of dockworkers at more than a dozen ports along the East Coast and Gulf Coasts are poised to walk off the job on Tuesday.