Prime Minister Justin Trudeau is urging Canada’s two largest railways and unionized workers to reach a deal to avert a strike that businesses warn will cause significant harm to the economy.

Canadian businesses are warning about potential long-term damage to the economy if railway and port strikes go ahead and choke the country’s vital trading arteries.

Canadian National Railway Co. issued a formal notice Aug. 18 that union-affiliated workers will be locked out in the coming days if a labor agreement is not reached.

Canadian National Railway amped up pressure on the Teamsters Canada Rail Conference to resolve an ongoing labor dispute with potentially wide-ranging impacts across North American supply chains.

Railway operator Canadian Pacific Kansas City Ltd. said a weakening economy and spate of labor disruptions weighed on freight volumes in the third quarter more than management anticipated.

CSX and CPKC railroads announced a deal June 28 that will allow them to beef up a little-used connection between their two networks in the southeastern United States to handle more freight.