Canada Post workers began a two-day strike in Hamilton, Ont. on Saturday, as their union tried to increase pressure during continuing negotiations with the postal service.

It is the second city hit by a rotating series of strikes that began Thursday night when workers in Winnipeg walked off the job. Service in Winnipeg resumed Friday night.

Canadian Union of Postal Workers president Denis Lemelin has said that workers in Hamilton will stay off the job through Sunday as part of the ongoing action across the country.

"We will continue to negotiate, but we must add pressure on Canada Post," Lemelin said on Friday.

The union said on Saturday that they will make decisions about additional strike locations based on progress at the negotiating table, adding that Canada Post had not yet responded to its most recent proposal.

The union is hoping to keep Canada Post from instituting changes it says would weaken health and safety measures.

For its part, Canada Post has said it needs to reduce labour costs because its lettermail business has dropped of by more than 17 per cent since 2006, as customers increasingly move to digital communications.

In addition to losing business to online services, Canada Post says it's also bearing a $3.2-billion pension deficit, leaving the corporation no choice but to address labour costs.

Canada Post's latest offer, which included cutting the starting wage to $19 an hour, has been rejected by the union. The offer would have also put a controversial short-term disability program on hold, at least temporarily. The union says that the starting wage would be cut by 18 per cent the current level.

Meantime, a spokesperson for Canada Post says the mail network continues to operate across the country despite the spot strikes. Anick Losier said that some 40 million pieces of mail were delivered Friday.

"Canada Post remains committed to negotiating a deal that is fair and reasonable without causing the corporation to become a drain on the taxpayers," she said in an email to The Canadian Press.

"We also believe that the union's strike activity is completely unnecessary. We are at the table and ready to negotiate."

So far the impact on consumers has been minimal, but the Canadian Federation of Independent Business says a stream of strikes could become a problem.

One group anxious to see a speedy resolution to the strike is charities that rely on mailed donations.

Ann Barnard Bell, development officer with Yonge Street Mission in Toronto, told CTV News Channel that she is concerned about having to cut services.

The mission, which provides services including keeping kids out of gang activity, takes in 70 per cent of its donations through the mail.

"Our hope is that people who have traditionally given to us through the mail would go online and make an online donation or telephone their donation in," Bell said on Friday.

The union's approximately 48,000 members have been in a legal strike position since May, when they voted 95 per cent in favour of striking.

In its proposal, the union is seeking a four-year contract with a guaranteed wage increase of 3.3 per cent in the first year, followed by 2.75 per cent increases in the next two years.

When postal workers last went on strike in the fall of 1997, their two-week job action ended with federal back-to-work legislation.

However long the strike lasts, both the union and Canada Post have promised Canadians who rely on the mail for certain monthly federal and provincial payments that they will still get their cheques.

On one day each month, Canada Post employees have volunteered to leave the picket lines to deliver Canada Pension Plan, Old Age Security and Child Benefits cheques.

With files from The Canadian Press