Canada Post says it's offer of June 25 is the last its going to make to postal workers.

The Crown Corporation admits that uncertainty around the current labour situation has led to a drop in the amount of mail going through the system and that's forced them to reiterate that the June 25 offer is the last.

They say the Canadian Union of Postal Workers have tabled a plan that would add $1 billion in new costs over the course of the agreement.

The union wonders why Canada Post is refusing to go back to the bargaining table, if Canada Post knows a disruption in service would hurt Canadians.

They says they're committed to remaining at the table to get a deal done.

So far neither side has given the required 72 hours notice of a strike or lockout.