President Joe Biden’s administration heaped pressure on U.S. port employers to raise their offer to secure a labor deal with dockworkers on strike for a second day on Wednesday, choking half the country’s ocean shipping.

After tens of thousands of dockworkers walked off the job at midnight, the Biden administration is confronting the complicated politics – and limited toolkit – of a work stoppage in the home stretch of a critical election season in which the economy has taken center stage.