SIMIC

"The work stoppage has begun, but CP and Teamsters are still at the table with federal mediators," Mr O'Regan said. "Parties are working through the night. We are monitoring the situation closely and expect the parties to keep working until they reach an agreement."

The stoppage means CP can't operate the railway and will create a "freight capacity crisis," CP said earlier this month in customer advisory.

The disruptions threaten to further roil supply chains and exacerbate volatility in fertiliser markets at a time when farmers are already having trouble getting key nutrients for crops for spring plantings. Crop-nutrient prices have skyrocketed, fueled by a global shortfall and worries that potential sanctions on Russia could disrupt global trade. Canada, along with Russia and Belarus, is a major supplier of the world's potash, a mined material used in fertilisers.

Some 3,000 engineers and conductors voted earlier in the month in favour of going on strike if a collective bargaining agreement isn't reached. The union is pushing for improved wages, benefits and pensions.

The lockout move comes after Nutrien, one of the top crop-nutrient suppliers, and Saskatchewan's government asked Canada's federal government to act swiftly to stop a strike.