MONTREAL -- The escalation of tension has just taken a new turn at the Port of Montreal as the longshoremen's union sent a 72-hour notice of an unlimited general strike to the Maritime Employers Association (MEA) on Friday.

Unless there is a last-minute change of heart, the 1,150 longshoremen will stop working at 7 a.m. on Monday, which would paralyze the port.

The union promised to maintain essential services and COVID-19-related shipments.

From that point on, the union, which is affiliated with the Canadian Union of Public Employees (CUPE), says the longshoremen will be on legal strike.

The longshoremen, who have been on an overtime strike and weekend strike since April 17 and 18, say they are responding to a change in their shifts that their employer wants to impose on them starting Monday, as well as job security issues.

"The only way we could answer that would be with a general strike on monday," said Michel Murray of the Longshoreman's Association.

The longshoremen earn on average $125,000 a year, but their shifts usually extend to 21 days in a row, and they have to remain available around the clock. They want more flexibility in scheduling. 

The longshoremen of the Port of Montreal have been without a work contract since December 2018. They launched a first strike last summer, which ended in a truce that lasted seven months.

Canadian businesses would be impacted just as the economy slowly recovers from the pandemic.

“It's actually the worse-case scenario that could happen,” said Jasmin Guenette of the Canadian Association of Independent Business.

The second-largest port in Canada, the employer claims that 90 per cent of all imported goods consumed in Eastern Canada go through the port. Rerouting containers to other ports come with extra costs.

The Quebec government also fears the impact of a strike.

“The Port of Montreal is an essential service for the relaunch of our economy. Now is not the time to paralyze the economy with a strike. Our businesses have already suffered enough from this labour conflict. The federal government has to intervene quickly,” said Quebec Economy Minister Pierre Fitzgibbon.

The longshoremen say they can still stop their strike if their employer returns to the table this weekend.

This report by The Canadian Press was first published April 23, 2021, with files from CTV's Stephane Giroux.