The union representing 2,700 train conductors and other workers at Canadian National Railway Co Ltd will not serve strike notice unless the company is intent on making drastic changes to their labor agreement, a union spokesman said.

Negotiators from the Teamsters Rail Conference, representing CN's train conductors, yardmen and traffic coordinators, and from Canada's biggest railroad are in talks to stave off a work stoppage.

"It is very unlikely that we will serve strike notice unless they change the terms of conditions," Teamsters spokesman Bryan Boechler told Reuters. He said the union's willingness to go on strike will depend how drastic the changes are that CN wants to make to the labor contract.

"Nobody wins with a strike," Boechler added.

The Teamsters issued a statement saying the union was pessimistic about the outcome of the talks. It accused CN of starting the countdown to a strike or lockout after it requested conciliation after only six days of talks.

CN said in a statement that it still hopes to sign a new contract without labor disruption through talks guided by a federal government-appointed mediator.

But getting a deal "will require some union flexibility and give and take," CN said.

Ninety percent of union members recently voted in favor of authorizing a strike if no agreement is reached. The two sides must now give 72 hours' notice of a strike or lockout.

The workers have been without a work contract since July 22.

Boechler said the union received a proposal from CN on Monday night, and handed its counter-proposal to the company on Tuesday. He said it hoped to hear back from CN later in the day.

CN said it wants to negotiate changes to union work rules but also wants labor talks over swiftly. As a result, it is prepared to accept the conciliator's recommendation of a three-year status quo agreement with no work rule changes if the union "endorses the deal and ratifies it quickly."

The union said that arbitration is not a viable option after an arbitrator was appointed to decide their last contract three years ago.

The union "is not willing to accept two consecutive arbitrated settlements that fail to address our safety and health concerns", it said in a statement.

CN said it has set up a contingency service plan in the event of a labor disruption. No CN operations in the United States will be affected, the company said. (Reuters)