Passenger train service across the country could be crippled if a brewing labour dispute between VIA Rail and 340 locomotive engineers isn't resolved by Friday.

On Tuesday, the union representing the engineers announced its intention to walk off the job at noon on July 24 if a deal isn't reached, VIA Rail said in a release posted on its website.

A mediator has been appointed to help bring management and the Teamsters Canada Rail Conference Union together, but the rail company said it has already been forced to alter its schedule.

"Unfortunately ... VIA has no choice but to begin to cancel certain departures of long-distance trains to ensure that passengers will not be stranded en-route in the event of a strike," the company said.

Long-haul routes between Vancouver and Toronto departing on July 21 will be terminated at Winnipeg, with all service on that route ending on July 24.

Dozens of other routes have also been altered or cancelled.

"In general, VIA will ensure that passengers departing prior to noon (EDT) this Friday are transported to destination, either by train or by alternate means," the company said.

"After noon this Friday, all VIA trains will be cancelled, until a settlement is reached."

For a full list of cancellations, visit VIA Rail's website or call 1 (888) 842-7245.