About 45,000 dock workers are poised to walk off the job at midnight Tuesday if a deal is not reached between the union representing the workers and the United States Maritime Alliance, which represents the ports.

A strike that is potentially just weeks away has the potential to have a weeks if not months-long impact on the U.S. economy.

Determined to thwart the automating of their jobs, about 45,000 dockworkers along the U.S. East and Gulf Coasts are threatening to strike on Oct. 1, a move that would shut down ports that handle about half the nation’s cargo from ships.