The union and two rail companies disagree on issues such as safety and scheduling.

The union representing workers at the Canadian National Railway (CN) says they will strike next week, in a new threat to the economy after promising to challenge a government decision to end an unprecedented rail stoppage.

The Teamsters union filed notice on Friday, just days after returning to work, that conductors, locomotive engineers and other workers at Montreal-based CN would strike on Monday.

The announcement is the latest twist in a labour dispute at Canada’s top two railroads, which locked out more than 9,000 unionised workers on Thursday, triggering a simultaneous rail stoppage that business groups said could inflict hundreds of millions of dollars in economic damage.

Labour Minister Steven MacKinnon, citing the risk to the economy, asked the Canada Industrial Relations Board (CIRB) on Thursday to order an end to the stoppage and also impose binding arbitration on the union as well as on CN and rival Canadian Pacific Kansas City (CPK).

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