The Public Service Alliance of Canada has pulled all 4,800 of the Parks Canada workers it represents off the job, escalating a three-week-old strike going into the summer's last long weekend.

The employees have been conducting rotating strikes at national parks, historic sites and other locations since Aug. 13 to support their demands for better pay.

Managers have been replacing workers during the sporadic walkouts so far.

In Montreal, picketing workers demonstrated Friday at the office of Stéphane Dion, the federal cabinet minister reponsible for Parks Canada.

Union spokesman Richard Coté said he was surprised when Dion agreed to meet with the union members for 10 minutes.

The minister listened to the union's explanation of its demands – a nine-per-cent pay increase over three years and permanent positions for some long-term casual employees – but made no promises, said Coté.

"I hope that Mr. Dion will talk to his caucus and say, 'Hey, let's go back to the table and negotiate a fair contract for these people,'" said Coté.

Bob Allen, a union representative helping staff a picket line in Ottawa on Friday, acknowledged the Parks Canada employees will lose some bargaining strength once the vacation season ends.

But he said other unionized federal workers will provide extra support within days.

"There are other units that are going to be on strike next week," Allen said, including 25,000 workers at the Canada Revenue Agency, who will be in a legal strike position Wednesday. "I'm sure that they'll help us, because if it was just Parks [Canada] by itself, it probably wouldn't have a lot of leverage after this weekend."

Allen said as many as 100,000 workers from Treasury Board, who will be in a legal strike position soon, and the Canadian Food Inspection Agency could also join the work stoppage in the weeks ahead.

"There's going to be a lot of people [off the job] in this town ... we'll probably have a problem figuring what we do with them all," he said.

Striking Parks Canada employees in Ottawa said their job action will shut down the Rideau Canal system from Friday to Sunday, but it will re-open on Monday.

Allen said boaters were given several days' notice of the walkout this weekend, so there aren't many left in the Rideau Canal.