Thousands of Canadian border workers could go on strike Friday if the mediation process fails to reach an agreement.
More than 9,000 members of the Public Service Alliance of Canada (PSAC) who work for the Canada Border Services Agency are expected to begin the strike at 4 p.m.
The two parties have been in mediation since Monday.
The union says key issues include pay parity with other law enforcement agencies, teleworking, retirement benefits and enhanced workplace protections.
The government maintains that 90% of front-line border agents are designated essential, meaning they cannot stop working during a strike.
But union members might resort to over-zealing, a tactic in which employees do their jobs exactly as outlined in their contracts.
Experts estimate that this could make each border crossing take longer than normal and thus cause massive disruption to traffic.