Canada’s two largest railroads, Canadian Pacific Kansas City (CPKC) and Canadian National, are beginning to shut down parts of their shipping networks due to an ongoing labor dispute with the Teamsters union, potentially leading to lockouts or strikes.

Both railroads have halted shipments of hazardous materials and refrigerated products, and CPKC plans to stop all shipments originating in Canada or heading there from the U.S. if no agreement is reached by Thursday.

The dispute, which centers on crew scheduling, rail safety, and worker fatigue, could severely disrupt cross-border trade, especially during the upcoming harvest season, NBC News has reported.

Although negotiations are ongoing, a work stoppage could have significant impacts on the supply chain, with railroads handling about 40,000 carloads of freight daily.

The trucking industry may be able to absorb some of the volume, but not all.

Written by B.C. Begley