Railroads and labor unions representing the industry’s workers are locked in heated contract negotiations. The two sides met with Labor Secretary Marty Walsh on Wednesday.

A spokesman for the railroads said there are no plans to lock workers out. However, if the two sides don’t reach an agreement by 12 a.m. Friday, workers could strike. If this happens, the impact on the already teetering U.S. economy could be disastrous. There are 12 unions representing rail workers. Most reached deals with the railroads earlier this week, but two of the largest unions are holding out over time off and quality-of-life concerns.

The unions called a new attendance policy by the railroads “draconian,” arguing workers could be terminated for taking time off to see a doctor. The railroads contend the time-off policy is more than fair for workers and balances the railroads duty to deliver goods all over the country.

Some shipments of hazardous materials were already diverted ahead of Friday’s potential shutdown. Virtually every industry in the country would be impacted in some way if a strike does happen. The White House called the strike “unacceptable.”

Nearly all ethanol, coal and grain in the U.S. moves by rail. Passenger and commuter lines would also be impacted by a strike. The Biden administration is working to line up alternate methods of delivery like trucks, planes and boats to keep the most critical chemicals and goods moving.

Even with those alternatives in place, though, economists said if the trains stop running, even for a day, it could take months to fully recover.

The Associated Press contributed to this report.