A potential freight railroad strike is looming. And retail leaders are starting to get nervous.

While 10 of the 12 unions representing railroads have reached agreements for new contracts with management, two outstanding unions, which represent engineers and conductors, still have yet to come to an agreement. In the event that the groups do not settle on a contract, a strike could commence as soon as Friday, which would mark the first national rail strike in 30 years. This would pose a series of problems for commuters as well as the already shaky supply chain situation ahead of the holiday season.

As the possibility of a strike grows more likely, American Apparel & Footwear Association president and CEO Steve Lamar has sent a letter to Congress, urging it to impose recommendations for resolution via the Presidential Emergency Board (PEB), which was created to help settle the dispute. According to the Association of American Railroads (AAR), a strike could cost the U.S. economy $2 billion a day.

“In the face of continuing supply chain issues and rising inflation, and with the all-important holiday season fast approaching, we again urge Congress to use its authority under Federal law to prevent any strike by imposing the PEB recommendations on all parties, thereby bringing these long-standing rail-labor negotiations to a quick and successful end,” Lamar wrote in a September 13 letter.

According to AAFA, a railroad strike would cause significant disruption to an already volatile supply chain, especially in footwear and apparel, where the vast majority of products are imported to the U.S.

“Rail, particularly intermodal, is an increasingly important piece of the puzzle as we work to bring the right clothes, shoes, and accessories to American families at the right time, and at the right price,” Lamar wrote.

Thomas Crockett, the VP of government affairs for the Footwear Distributors & Retailers of America (FDRA), also noted his organization’s concern with the possibility of a rail strike.

The National Retail Federation released a similar statement on Wednesday and last week urged Congress to implement the recommendations of the PEB to avoid a strike as well.

“Freight rail is critical to the retail supply chain, and retailers of every size rely on it to move cargo every day,” president and CEO Matthew Shay said in a statement on Wednesday. “Retailers are deeply concerned about the situation and the impact that a disruption would have on business operations throughout the country.”

In joint Sunday statement from the leaders of the two remaining unions — the SMART Transportation Division and the Brotherhood of Locomotive Engineers and Trainmen — both unions emphasized the need for improvements to working conditions, including ending drastic penalizations for engineers and conductors who get sick or visit a doctor.

“Our members are being terminated for getting sick or for attending routine medical visits as we crawl our way out of worldwide pandemic,” the unions said.

A strike could impact “more than 7,000 trains daily,” result in retail product shortages, and disrupt “hundreds of thousands of passengers” on railroads, according to a statement from the AAR.

“As the freight sector heads into peak shipping season, a nationwide rail work stoppage would result in an unnecessary $2 billion daily economic hit,” said AAR president and CEO Ian Jefferies in a statement. “President Biden’s PEB recommended terms that would maintain the highest quality health care coverage and result in compounded wage increases of 24%, bonuses totaling $5,000 — the highest pay increases in nearly 50 years.”