MONTREAL - Striking CN conductors and yard service workers will call off their national strike if the Canada Industrial Relations Board rules that the work stoppage is illegal, the union's chief negotiator said Monday.

"If the board rules (Tuesday) that it is an illegal strike and they issue a back-to-work order, we'll comply with that and get back to work immediately," Rex Beatty said in an interview.

CN filed a complaint with the federal labour board on Saturday after nearly 3,000 United Transportation Union workers walked off the job across Canada after negotiations broke down.

The company argues the union's pressure tactic is against the law because the UTU International -- the certified bargaining agent for the employees -- has not authorized the strike.

Workers counter that Canadian law governing strikes isn't bound by the international union's internal process.

"So the question to be decided is, did the union follow the various steps under Canadian law -- the Canadian Labour Code -- to reach a point where not only could they strike, but allows them to strike," Beatty said.

"And if you walk through the code, everything was absolutely in order."

The strike hasn't affected Via Rail service or commuter trains in Montreal and Toronto.

CN argues the union's financial demands are excessive.

"We must achieve a settlement that is economically sustainable to the company," said CN spokesman Mark Hallman.

"The union's demands were, in terms of wages, excessive and out of line with other private sector settlements that have been recently negotiated by the company and also within the larger private sector."

Workers are seeking a wage increase of 4.5 per cent over two years, along with a four-per-cent increase in the third year of the contract. That's in addition to $1,000 per year over three years.

Non-monetary issues include longer lunch breaks, excessive investigations of personnel and the threat of pensions being slashed if an employee is fired.

CN shares gained 21 cents to $53.31 midday in trading Monday on the Toronto Stock Exchange.