Protesters started collecting on Parliament Hill on Sunday, taking part in protest training sessions ahead of a planned mass confrontation with the federal government over its support for the oilsands and a proposed pipeline from Alberta to Texas.

Hundreds of environmentalists are expected to turn out for Monday's mass rally, which organizers expect will become "the largest civil disobedience action in the history of Canada's climate movement."

The gathering comes about a month after thousands of demonstrators risked arrest in Washington by protesting the Keystone XL pipeline in a massive sit-in outside the White House. More than 1,000 protesters including actress Darryl Hannah were arrested during the rally.

In a display of unity, environmentalists in Canada also plan to risk arrest when they sit outside the nation's most prominent government building on Monday.

Mandatory training sessions were held in Ottawa on Sunday, meant to teach protesters how to safely demonstrate.

A message posted to Ottawa Action's webpage stressed the importance of the sessions.

"Because we are dealing with an arrestable situation it is incredibly important that everyone is on the same page, understands the action, legal consequences and the basics of non-violent direct action," the post read.

Environmental advocate Rosemarie Whalley travelled to Ottawa from Montreal for the protest. She and about 150 others arrived one day early for training sessions.

Whalley said if the Keystone XL pipeline is approved, there will be dire consequences for the environment.

"What we see ahead is a catastrophe -- a catastrophe for our grandchildren and their grandchildren," she told the Canadian Press.

The ongoing fight against oil

Environmentalists have condemned Canada's oil and gas industry, accusing oil companies of emitting excessive amounts of carbon during extraction and producing so-called "dirty" oil.

Proponents, on the other hand, argue that Alberta's oilsands and TransCanada Corp.'s Keystone XL pipeline will encourage job growth and stimulate the economy.

Prime Minister Stephen Harper supports the pipeline and continues to defend it amid a flurry of opposition. Last week, he told reporters in New York that the pipeline was a "no brainer" because it would generate thousands of jobs and ensure the United States would have a secure source of oil.

Oilsands employment is expected to grow from 75,000 jobs to 905,000 positions by 2035, according to numbers from The Canadian Association of Petroleum Producers. About 126,000 of those jobs will be outside Alberta. Details on whether the jobs will remain in Canada were not immediately available.

U.S. officials are expected to make a decision on the Keystone XL pipeline by the end of this year.

Because the cross-border pipeline is already approved in Canada, organizers say Monday's protest will focus more on the need for the federal government to turn away from oilsands energy.

Representatives from groups such as Greenpeace Canada, the Council of Canada and the Indigenous Environmental Network (IEN) will be present at Monday's rally asking the government to invest in renewable energy.

Some protesters have said they are willing to breach police barriers in order to have their message known.

The RCMP, which is responsible for security on Parliament Hill, will be working with local police to keep the peace during the demonstration, said spokesman Sgt. Marc Menard.

Menard would not specify what would happen if protesters wandered beyond police boundaries.

With files from The Canadian Press