Employers at ports in British Columbia will lock out unionized supervisors, a move that threatens to freeze trade on Canada’s West Coast and add to the country’s supply chain disruptions.

Dock employers in British Columbia plan to shut out workers Monday in response to a union's strike notice, grinding trade to a halt at Canada's busiest and third-busiest ports.

Employers at Canada’s largest port have said they would lock out their workers after a negotiating deadline with the union had passed, potentially disrupting key shipments of the country’s coal, potash and beef.