Confronted by the militancy of longshore unions, port operators have deployed automation, in part to limit their vulnerability to labor troubles. Not coincidentally, dockworkers tend to look suspiciously at robots and other forms of innovation, divining threats to their livelihoods.

With a dockworkers' strike threatening to close ports on the East and Gulf coasts beginning this week, Chris Butler is growing worried. Butler is CEO of the National Tree Company, and, like many businesses,

It is growing ever more likely that tens of thousands of dockworkers in contract negotiations will soon go on strike, snarling up supply chains and costing billions of dollars just weeks before the election.

Tens of thousands of US dockworkers plan to strike next week if there is no breakthrough on contract talks, just a month before November's closely contested presidential election.

Some 25,000 dockworkers at East and Gulf Coast ports may strike as early as October 1 if their union doesn't reach a contract deal with shipping companies and port operators.