MONTREAL - The Canadian Auto Workers union has given CN Rail a strike deadline.

The CAW says 3,975 of its members employed by Canada's largest railway are set to walk out first thing Tuesday morning.

The workers are in four bargaining units -- mechanical, clerical/intermodal, excavator operators, and owner-operator truck drivers.

Their last contract expired on Dec. 31.

Mark Hallman, CN's director of communications, says contract talks are continuing in Montreal, and the railway remains hopeful a settlement will be reached before the strike deadline.

However, if there is a walkout, Hallman says management personnel will step in to keep the railway operating "safely and as efficiently as possible."