Hamilton is being targeted this weekend  by striking postal workers, the second city to be hit by  rotating work stoppages across the country.

Workers in Hamilton were to picket from late Friday until Sunday night.  On Thursday, postal workers in Winnipeg walked off the job at midnight for a 24-hour strike after rejecting last-minute contract proposals by Canada Post.

Despite the walkout, "it’s pretty much business as usual today across our network," Canada Post spokesperson Jon Hamilton told CBC News in an email.

"Even in Winnipeg, things are still open. We haven’t sealed anything in Winnipeg at this time. I just don’t want people to think we’ll shut things down during the union’s rotating strikes."

The Canadian Union of Postal Workers said in a statement that they met with representatives of Canada Post on Friday morning and "provided our response to their most recent proposal. Management is currently considering our position."

Earlier in Ottawa, the president of CUPW clarified the reasons for the strike.

"We're on strike in Winnipeg because we want to continue to put pressure on Canada Post and really force the corporation to resolve the concrete problems for workers on the work floor,"  Denis Lemelin said. "We cannot agree to work in conditions that are not safe."

Winnipeg was chosen for the first strike activity because it was the first city to be affected by Canada Post's modernization program, which Lemelin said causes safety concerns and has resulted in a 15 per cent increase in injuries among workers, as well as a sharp decline in customer service.

New methods include requiring letter carriers, who walk on average 15 kilometres a day, sometimes in bad weather, to carry multiple bundles on their routes instead of just one. Inside workers stand for eight-hour shifts at new machines that are twice as fast at processing the mail.

In an interview with CBC News, Hamilton defended the new methods and said the Crown corporation has met almost weekly with the union over these changes since 2008.

"The equipment we're bringing in and have brought in and using successfully is used safely by postal systems around the world and has been for years," he said.

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"The methods of carrying mail in two bundles rather than just one is used by 200,000 letter carriers in the U.S. every single day and done safely. It wouldn't have been continued for 20 years if that wasn't safe."

In a news release Friday, Labour Minister Lisa Raitt said she was concerned about the effect a strike would have on Canadians and businesses across the country.

"Our government is disappointed that the parties have so far been unable to reach an agreement and that the union has felt it necessary to begin strikes. …The best solution is the one that the parties reach themselves."

Proposed changes to sick leave have been among the key sticking points for the union.

On Thursday, Canada Post made what it said were a number of compromises on issues, including sick days and the wage for new hires. But CUPW said the agency didn't offer anything on "the major outstanding issues" and initiated the strike.

In the event of a nationwide strike, Canada Post will cease nearly all mail delivery, with the exception of monthly social assistance payments such as old age security and veteran's cheques, as well as welfare and child benefit cheques. People can call 1-800-OCANADA for more information.

Those cheques will all be delivered in one day by letter carriers in uniform who had agreed in advance to be on the job through a work stoppage, Hamilton said. Some retail postal outlets will remain open, he added.

The federal government has warned that a postal strike could harm the Canadian economy.

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Canada Post workers last went on strike in 1997 and were out for two weeks before being legislated back to work.

While a postal strike in 2011 won't have the same impact as those in the 1980s or 1990s, "mail delivery is still a life-line to small business, rural communities, seniors and charities who rely on mail campaigns to raise money," Hamilton said.

Rotating postal strikes won't have as much impact on businesses as a national strike. But a steady stream of such strikes would cause problems, Dan Kelly, the Canadian Federation of Independent Business senior vice-president, told The Canadian Press.

"It inevitably is going to throw some wrenches into the system and cause delays at the very least and a lot of stress and anxiety with small businesses."

The Red Cross, for example, which is trying to raise $1 million to fund community projects through a lottery, said in a news release that "a strike will gravely affect the final week of ticket sales, and the final outcome of the 2011 Red Cross Lottery."

Canada Post had tabled an offer that included a defined benefit pension plan for both new and existing employees, up to seven weeks vacation and job security.

But after more than seven months of contract talks, the union rejected Canada Post's final offer and tabled its own counter-offer on Monday.

Canada Post called the union's offer "out of touch" with the challenges currently facing the Crown corporation, which includes a core letter mail business that has fallen by more than 17 per cent per address since 2006, and a pension deficit of $3.2 billion.

The union, which represents close to 50,000 letter carriers and other workers, is asking for a four-year contract with wage increases of 3.3 per cent in the first year and 2.75 per cent in years two and three. Sick leave and pensions are also issues.

The average starting wage for postal workers is $23 an hour.