Union members representing Canadian Pacific Railway Ltd's (CP) conductors and locomotive engineers have served a notice to go on strike as early as May 29, according to a union statement released on Saturday.

The strike notice comes a day after the union rejected the company's latest contract offer.

"After workers at CP voted to reject the last contract offers, the company is still refusing to negotiate seriously," the statement said. CP is the country's second-largest railroad.

Some 3000 conductors and locomotive engineers voted 98.1 percent to reject CP's final offer on Friday, while about 360 signals and communications employees voted 97.2 percent to authorize strike action, the statement said. Commuter train services would not be affected in the event of a strike by Teamster members.

CP will continue to meet with union members in the hopes of reaching agreements, the company said in a statement, adding it has started its contingency plan to ensure a smooth and safe wind down of operations.

The labor strife comes at a time of tighter rail capacity in Canada, with CP and rival Canadian National Railway facing strong demand for shipments of grain, potash and other commodities.

The union members are committed to working with federal mediators to reach negotiated settlement and are willing to remain at the bargaining table until the May 29 strike deadline and beyond, the statement added.

The workers, whose collective agreement expired late last year, are asking for more predictable schedules to combat crew fatigue, among other demands.