MONTREAL -- Canadian National Railway, Canada's largest rail carrier, could soon see freight operations brought to a standstill if it doesn't reach a new labor agreement soon, one of the railway's main unions said on November 23.

A wire service reports that members of the United Transportation Union, which represents about 4,500 conductors and yard personnel at CN, have voted 90 percent in favor of a strike mandate, the union said.

"Union members have given us a strong mandate to take strike action if negotiations with CN Rail do not soon show some results," said Guy Scarrow, vice-president of the UTU.

But the company played down the risk of an imminent strike, saying the union first must get the approval of Canadian labor authorities over the level of rail services that would be maintained in case of a work stoppage.

The main issues in the dispute are retroactive pay and a "compliance incentive clause" that would set fines for management if it violates the agreement, said Scarrow. The latest three-year agreement expired last December.

A strike would only target the railway's Canadian operations, since the union represents only CN workers in Canada. But the company's operations in the United States would be seriously squeezed because of the extensive cross-border rail activity between the two countries, Scarrow said.

CN is the fifth largest railway in North America.

The union said it has proposed maintaining passenger rail services in Toronto, Montreal and in remote areas of the country. Only freight traffic would be affected, it said.

But shutting down the cargo operations would nevertheless cripple CN as it derives the lion's share of its revenues from shipping goods across its coast-to-coast network and into the United States.

CN spokesman Mark Hallman played down the strike threat, saying any stoppage would have to be authorized by the Canada Industrial Relations Board, which has yet to set a date for a hearing with both parties.

"There is no imminent potential labor disruption," Hallman said. "We remain optimistic."

The last strike at CN was in 1995 and was ended by back-to-work legislation.