Picketing Parks Canada workers are slowing the flow of visitors to some of the country's historic sites and national parks and have closed at least two sites.

Parks officials say there's no need for travellers to change their plans because of the strike. Gaby Fortin, director general for Parks Canada Western and Northern Canada, says the national parks in his region are open and will remain so during the weekend.

But the Parks Canada website says pickets have already shut down the Fortress of Louisbourg, a reconstructed 18th century French fortress in Cape Breton, Nova Scotia.

The Rideau Canal, 200-kilometre Ottawa-area waterway, is also closed, officials with the Public Service Alliance of Canada union say.

Kevin King, the union's regional vice-president, says there could be rotating work stoppages, disruptions at some facilities, or campgrounds could be closed

"People need to be prepared that there's a labour disruption out there," King warns.

"It will be on a strategic basis and some parks in certain parts of the country will be hit harder than others."

Fortin says it is illegal for pickets to block public access to campgrounds. He says if the gates of the parks are picketed, the agency would waive the fee and let visitors go through.

Parks visitors can find out the status of any park by calling toll-free 1-888-773-8888.

The staff went on rotating strike Friday morning following days of fruitless negotiations between Parks Canada and its employees' union.

PSAC, the union representing 4,800 parks employees, met with the federal agency all day Wednesday and Thursday. But talks broke down after the union rejected Parks Canada's latest offer.

"We tried hard to reach a tentative agreement by moving significantly from our previous position and acknowledging the recommendations of the conciliation board," said Jeannie Baldwin, the officer overseeing negotiations.

"But the employer hasn't moved by much from their position in the last two days -- basically they came, tabled a minor improvement on their pay position and shut down."

The main stumbling block is wages. The union has proposed salary increases of three per cent in each of three years, retroactive to Aug. 5, 2003, when the union's contract expired. They also want a reduction of the wage gap between Parks Canada workers and their private sector counterparts.

But the government says that when all of the union's economic proposals are taken together, including the salary increase, the total raises being asked for is nearly 34 per cent for wardens, 39 per cent for canal workers and 43 per cent for general labourers over three years.

Fortin says overall, the government agency is proposing a nine to 10 per cent increase over a three-year period.

The last labour disruption in Parks Canada was in 1991.