Quebec City and Kitchener, Ont. are the next two targets of the ongoing, rotating postal strike, the union announced on Thursday, as Canada Post said the two sides remain far apart on a number of issues.

Around 1,550 members of the Canadian Union of Postal Workers union will hit the picket line in the two cities for a 24-hour work stoppage starting at 11 pm ET.

"These locals were chosen because both have experienced major cutbacks as a result of [Canada Post] management's cost cutting crusade," the union said in a statement Thursday night. "Quebec City has witnessed the closure of its mail processing plant and Kitchener has seen the transfer of its parcel operations to Toronto."

The union said workers will return to work Thursday night and Friday morning after striking at 13 small to mid-sized communities.

Meanwhile, Canada Post accused CUPW of rejecting major compromises proposed by the Crown corporation to address sick leave and staffing levels.

"Canada Post and CUPW remain far apart on several fundamental issues," it said in a news release.

"The strike actions being orchestrated by the union are seriously damaging the financial viability of the company. The rotating strikes have damaged Canada Post and clouded the company's future. Volumes at Canada Post have fallen significantly since the union started rotating strikes on June 3."

Canada Post also said it will cut mail delivery in urban centres to three days a week starting Monday.

Carriers will deliver letters only three days a week: Monday, Wednesday, and Friday, said Canada Post spokesman Jon Hamilton.

Those affected in urban centres include people who would normally get their mail delivered by a uniformed letter carrier with a mailbag. Those living in rural areas who typically get their mail from carriers not in uniform, driving their own cars, are not affected by the reduction.

Hamilton said the move comes because mail volumes have dropped by half since last Thursday, when postal workers began a series of rotating strikes.

Canada Post will also cut staffing levels at its mail sorting plants and pay unionized letter carriers only for the three days they work, Hamilton said.

"This is all as a result of the 50 per cent drop we've seen in our volumes in the last five days due to the union's rotating strike activity," Hamilton said.

Earlier, Hamilton repeated the company's position that the strikes aren't necessary because union and Canada Post negotiators continue to talk — although there hasn't been much progress and many issues.

"The union keeps saying they're having rotating strikes because they want to get the company to the table. We're at the table," Hamilton said.

"But we're not at the table to discuss adding a billion dollars of labour costs over the next four years, we're not at the table to discuss stopping any efforts under way to modernize this company and secure our future. That's not what we're there to talk about. We're there to talk about generous terms and conditions for the next four years that will make our employees better off than they are today."

Canada Post has said its latest offer includes annual wage increases that for current employees would bring the top wage rate to $26 an hour, job security, no changes to a defined benefit pension plan, medical benefits and "generous" vacation leave that tops out at seven weeks per year.

Future hires would get a starting wage of $19 an hour, rising to a maximum $26 an hour, up to six weeks vacation and a defined benefit pension by age 60.

Rotating strikes began last Friday in Winnipeg and have since been held in Hamilton, Montreal, Moncton, N.B., Victoria, Calgary and Edmonton.

With files from The Canadian Press