Up to 140 CN locomotive engineers in Winnipeg could be on strike by this weekend.

They are among 1,700 engineers across the country whose union, Teamsters Canada Rail Conference, served the company with strike notice on Wednesday.

The notification prompted federal mediators to call a meeting between the union for the engineers and CN in an attempt to avert a strike that could come as early as one minute after midnight this Saturday morning.

The mediators have called the meeting for Friday in Montreal.

The engineers' last contract expired on Dec. 31, 2008.

Clay Finch-Field, the chair of the Teamsters local in Winnipeg, said the workers are looking for what the union calls industry standard wage and benefit increases.

But, he said, the labour dispute is not really about money. Instead, it's about working conditions.

Finch-Field said CN arbitrarily moved to change the engineers' working terms, giving them almost no notice of shift changes. Other sticking points include the company's unwillingness to be flexible in its scheduling, he said.

In a statement on Wednesday, CN called the union's strike notice "unfortunate because a strike is in no one's interest — not the locomotive engineers, CN's other employees, its customers or the Canadian economy."

Winnipeg is a major hub for CN and one of the three largest terminals in Canada.