The federal government urged Canadian National Railway Co. and its striking workers to continue talks in what it believes would be the fastest way to resolve their dispute which has stopped freight trains across the country. The strike at the country's biggest railway entered its fourth day with no resolution in sight as round-the-clock negotiations continue under the watch of federal mediators. The Teamsters union said Friday that "no substantive progress has been made" since 3,200 workers hit the picket lines early Tuesday morning.