HARRISBURG, Pa. (WHTM) – Amtrak has no scheduled passenger rides between Harrisburg and Pittsburgh as the possibility of a strike looms.

Routes from Harrisburg to Philadelphia and through the northeast corridor appear to be unaffected. Amtrak says Keystone Service between New York and Harrisburg will not be affected.

According to Amtrak, in the northeast between Boston, New York, and Washington D.C. there will be no impact on Acela, and “only minimal changes are expected in the Northeast Regional services.”

Amtrak uses freight tracks for its long-distance trip, so several of those routes are now canceled in case they get blocked by freight trains.

Commuters, food producers, refineries and others could all be affected if there is a nationwide rail strike at the end of this week.

The Biden administration was putting pressure on railroads and unions Wednesday to settle their differences and avert a strike. But just in case that doesn’t work, the administration was also working on a plan to use trucks and planes to move goods that are normally carried by freight railroads.

“Amtrak is closely monitoring ongoing freight rail management—labor contract negotiations. While these negotiations do not involve Amtrak or the Amtrak workforce, many of our trains operate over freight railroad tracks. Because the parties have not yet reached a resolution, Amtrak has begun to make initial service adjustments in response to a possible freight railroad service interruption that could occur later this week. If your train is canceled, we will attempt to notify you at least 24 hours in advance at the contact information you provided when making a reservation—as well as offer the opportunity to receive a full refund.”

The nation’s biggest freight railroads began negotiating with a dozen different unions representing about 115,000 workers in late 2019, but talks were slowed by the pandemic, which limited face-to-face meetings.

Many of the unions have reached tentative agreements with the railroads, but two large unions representing engineers and train conductors have held out for better terms.

Government mediators tried to broker agreements, but that didn’t work. President Joe Biden then appointed a presidential emergency board, which held hearings and issued recommendations last month that included 24% pay raises and thousands of dollars in bonuses.

By federal law, the unions can’t legally strike until after Friday morning, just after midnight. That’s when a 30-day “cooling-off” period ends, under terms of a law called the Railway Labor Act, which governs contract talks in the railroad and airline industries.

Congress could intervene and impose settlement terms, as it has done in previous nationwide rail-labor disputes.

Lawmakers could adopt the recommendations of the emergency board, or they could order additional negotiations or arbitration to settle the standoff.

Rail workers stayed on the job throughout the pandemic but have not received a raise since 2019.

The unions sought raises of 31% over the five-year term of the new contracts, while the railroads offered 17% before the emergency board’s recommendations. The largest railroads endorsed the board’s middle-ground proposals, and most of the unions have reached tentative agreements based on those details.

However, the Brotherhood of Locomotive Engineers and Trainmen, and the transportation division of the International Association of Sheet Metal, Air, Rail and Transportation Workers, which represents conductors, have held out in hopes of better terms. They want railroads to increase staffing — the major railroads have cut nearly one-third of their jobs in the last six years — and to ease strict attendance policies that make it difficult to take time off.

Railroads such as Union Pacific, BNSF, CSX and Norfolk Southern carry cars, coal, chemicals, grain, imported goods and other products and raw materials throughout the country. A shutdown — even a brief one — would delay critical shipments and ripple across the economy.

The Association of American Railroads trade group estimates that a strike would cost the economy $2 billion a day.

Congress is widely expected to block a strike if it comes to that, but it is not clear how quickly lawmakers would act.

About 300,000 barrels of crude oil is shipped by rail every day, and refineries might have to slow production if deliveries are delayed, according to the American Fuel & Petrochemical Manufacturers. Analysts warn there could be shortages of gasoline and diesel in some places such as the Northeast.