TORONTO - Canada's labour minister is urging the union representing striking Canadian National Railway locomotive engineers to accept binding arbitration as management tried to keep the trains running Saturday.

In a statement, Rona Ambrose said Saturday she's "disappointed" the Teamsters union and CN couldn't reach an agreement before some 1,700 engineers across the country walked off the job Friday at midnight.

Ambrose said CN has already agreed to binding arbitration and that the government is ready to appoint an arbitrator once the union gives its approval.

She vowed not to support the labour disruption at a time when Canada's economy is still recovering.

The Teamsters did not immediately respond Saturday to Ambrose's call for binding arbitration.

The union has said a strike could have been postponed had the railway, Canada's largest, agreed to negotiate and not impose a 1.5 per cent wage increase and new mileage caps.

CN made contractual changes after three days of negotiations broke off Nov. 20 following 14 months of talks.

The Teamsters Canada Rail Conference responded by issuing a 72-hour strike notice -- saying CN was effectively locking out employees by unilaterally changing the terms of the collective agreement.

TCRC president Daniel Shewchuk said in an interview earlier Saturday that while the union made "substantial movement" during Friday's talks, the railway wouldn't budge.

"We got very little, if nothing, back from the company, which basically drew the line in the sand," Shewchuk said Saturday.

The union has said that raising the mileage cap -- the maximum distance engineers can travel in one month -- by 500 miles to 4,300 miles would require some workers to work seven days a week, with no time off, and cause layoffs.

CN says its locomotive engineers work on average 37 hours a week, and the new cap would increase that to approximately 41 hours. Engineers would also work an average of 16 to 18 days per month, up from 15 to 17 days under the old cap, the railway has said.

A prolonged strike could affect "any of the customers that ship by rail across Canada," including the auto sector, said Shewchuk.

The work stoppage could also negatively impact grain shipments in western Canada.

The union was making "excessive demands" and CN's proposals were reasonable, said communications director Mark Hallman.

Supervisors and managers who are qualified engineers were taking over operation of the locomotives to minimize any freight service disruptions, Hallman said.

It was not clear how many trains were operating Saturday, Hallman said in an email that details of CN's operationg plan during the strike were confidential.

"I can tell you today CN executed well on the plan," Hallman's email said.

Industry analysts have said managers could keep CN operating, though perhaps not at 100 per cent.

The strike was not expected to affect Via Rail passenger service or commuter rail service in the Montreal area.