The union representing Canada Post's urban workers gave the Crown corporation an ultimatum Monday that it will go on strike this week if its final offer is rejected.
Denis Lemelin, national president of the Canadian Union of Postal Workers, said the notice puts the union in a legal position to strike on Thursday at 11:59 p.m. ET after it turned down the latest offer from Canada Post.
"We have some days in front of us but at some point the union will have to go forward," Mr. Lemelin said after meeting with Canada Post on Monday morning.
"It is important that Canada Post let go some of its demands and rollbacks that they put on the table."
Mr. Lemelin said the union and Canada Post have a history of reaching a deal at the last minute, but said Canadians thinking about mailing a bill payment or other urgent letter this week will have to consider that decision carefully.
"It is why we have informed the population around the issue and people have the choice to use or not to use the mail," he said.
Federal Labour Minister Lisa Raitt was concerned a strike was being considered and urged the two sides to reach a negotiated settlement.
"Any work stoppage would impact Canada's economic well-being," Ms. Raitt said in a statement.
"We are currently going through an economic recovery, which remains fragile."
The two sides have been in talks for more than seven months and have not been able to hammer out an agreement. CUPW made a final offer Monday that includes several amendments and clarifications to its positions - including a drop in its wage increase demands.
The union represents about 50,000 urban postal workers and negotiations to reach a new collective agreement began last fall.