JPMorgan estimates the economic loss from the shutdown of every major container port from Houston to Miami and New York-New Jersey will be between $3.8 billion and $4.5 billion per day.

The union representing U.S. dockworkers signaled that 45,000 members will walk off the job at midnight, kicking off a massive strike likely to shut down ports across the East and Gulf coasts

Transportation and warehousing sectors are poised to first feel the pinch, with a broader economic fallout expected if the strike drags on.