MONTREAL -- The union representing safety and maintenance workers at Canadian Pacific Railway issued strike notice on the company Thursday and could be off the job by the weekend if negotiations on a new contract fail.

The 1,800 workers, represented by Unifor, said if a deal cannot be reached by midnight Saturday, their members will be off the job.

It comes after the Teamsters Canada Rail conference union, representing 3,300 locomotive engineers conductors, trainmen and yardmen across Canada, served CP with the same deadline.

The labour strife could hamper freight service across the country, but negotiations with both unions are ongoing in Montreal this week with the help of federal mediators.

Unifor's national rail director Brian Stevens said the two sides remain far apart on the issues, which include working conditions, representation, health and safety.

"Anything is entirely possible. Our intention here is to bargain a negotiated settlement," Stevens said.

"We have a long way to go, and there's a short time to get there."

In the event of a strike, Canadian Pacific said this week it would "implement its extensive contingency plan by deploying qualified management employees to maintain a reduced freight service on its Canadian network."

The Unifor workers perform safety inspections on all rail cars and locomotives, as well as maintenance and repairs on trains.

Stevens said that in his opinion, a strike would have an immediate impact on locomotive availability and the overall safety and maintenance of the fleet.

"The locomotive fleet will be impacted because the bulk of our employees at CP rail are tradespersons," he said. "There are safety standards to both the locomotive fleet and the rail cars, and our members are the professionals who are trained and qualified safety and maintenance professionals."

A spokesman for the Teamsters suggested this week any disruption of rail service would have a widespread effect on industries that rely on trains, and that CP managers and other staff would be hard-pressed to operate trains and maintain service.

In 2012, the federal government passed legislation to force an end to a nine-day strike by some 4,800 striking members of the Teamsters union and CP Rail employees.

At the time, then-labour minister Lisa Raitt said a prolonged strike would cost the Canadian economy $540 million a week.

There are also separate negotiations taking place between the two unions and Canadian National Railway, but neither union in the CN talks has taken a strike vote.

The Teamsters also issued a warning on Thursday that commuter rail service in the Montreal area could be affected as early as Sunday morning.