Workers on the Canadian side of the St Lawrence Seaway have launched a strike that has shut the waterway linking Great Lakes ports to international markets.

The Unifor union said the strike began on Saturday night after contract talks with St Lawrence Seaway Management Corp, which manages 13 of the 15 locks on the US-Canadian system of canals, failed to result in an agreement.

“The parties are at an impasse as Unifor continues to insist on wage increases inspired by automotive-type negotiations, while the SLSMC [St Lawrence Seaway Management Corp] works to find a fair and competitive labour agreement that balances wage demands and market realities,” the not-for-profit company set up by the Canadian government said.

“As a result, the system will remain shut down until an agreement can be reached, whether it be temporary or tentative, as we work diligently to minimise disruption for all stakeholders.”

Union national president Lana Payne said she was disappointed by the lack of movement by the management company.

“This impasse is extremely unfortunate, but our members remain committed to getting a fair agreement,” she said.

Unifor issued a 72-hour notice to strike on Wednesday and Quebec union director Daniel Cloutier said it continued to negotiate up to the last moment.

“But we cannot allow workers’ rights to be compromised,” he said. “We remain open to discussion and hope that the employer will reconsider its position for the good of all.”

Terence Bowles, president and chief executive of St Lawrence Seaway Management Corp, said the outfit is dedicated to finding a solution in the interests of both employees and the corporation.

“In these economically and geopolitically critical times, it is important that the seaway remains a reliable transportation route for the efficient movement of essential cargoes between North America and the remainder of the world,” he said.

The seaway system’s users include bulkers, tankers and other cargo vessels that move cargoes to and from US and Canadian ports including Duluth, Chicago, Toronto, Cleveland, Toledo and Milwaukee.

The strike comes at a key moment for the Canadian grain export season, which typically peaks in late summer and early autumn.

St Lawrence Seaway Management Corp has applied to the Canada Industrial Relations Board seeking an order that Unifor should provide workers to allow grain cargoes to continue to flow.

Adam Tindall-Schlicht, the administrator of the US government’s Great Lakes St Lawrence Seaway Development Corp, said the US-managed section of the seaway is also closed during the strike.

“The Great Lakes St Lawrence Seaway Development Corp team worked to ensure a safe close of Eisenhower and Snell Locks in Massena, New York, and notified cargo operators of impacts,” he said on LinkedIn.