The U.S. Postal Service has temporarily suspended accepting mail headed to Canada due to the strike by Canada Post workers.
It is asking customers to refrain from mailing items addressed to Canada, until further notice.
The move by the U.S. Postal Service comes after some 55,000 Canada Post workers walked off the job more than two weeks ago.
Canada Post says it has presented the union with a framework to reach negotiated agreements in the dispute that is threatening the busy holiday season.
It says the plan includes proposals to bring greater flexibility to Canada Post’s delivery model and shows “movement on other key issues” in the labour dispute.
The Canadian Union of Postal Workers says its negotiators are reviewing the proposal.