Teamsters Canada says if Canada Post workers go on strike or are locked out, its members at Purolator won't handle any packages postmarked or identified as originating from the carrier.
Spokesman Christopher Monette said in an email that the Canadian Union of Postal Workers has the Teamsters' full support, and that they believe good union jobs are essential pillars of Canadian society.
Workers at Canada Post could be on strike in the early hours Friday.
Meanwhile, Canada Post could lock out workers as early as 8 a.m. Eastern Friday but has said it doesn't intend to do so.
Canada Post says its operations will continue if there are rotating strikes, but delays may occur.
The postal workers' union has said that after almost a year of bargaining, the parties still remain far apart on many issues.
