Canadian National Railways Conductors, train personnel and yard workers have given strike notice ahead of a Tuesday deadline.
The union, which represents 3,200 workers, provided the 72-hour notice today as contract negotiations continue over the weekend.
They warned in October that they were prepared to launch job action after over six months of unsuccessful talks.
A strike could begin at 12:01 a.m. Tuesday now that the notice has been provided.
The company says its offer to enter into binding arbitration was declined by the union. The workers have been without a contract since July 23.