First Nations communities from Canada and the northern United States signed a treaty on Thursday to jointly fight proposals to build more pipelines to carry crude from Alberta's oil sands, saying further development would damage the environment.

The treaty, signed in Montreal and Vancouver, came as the politics around pipelines have become increasingly sensitive in North America, with the U.S. Justice Department intervening last week to delay construction of a contentious pipeline in North Dakota.

The Treaty Alliance Against Tar Sands Expansion was signed by 50 aboriginal groups in North America, who also plan to oppose tanker and rail projects in both countries, they said in a statement.

Targets include projects proposed by Kinder Morgan Inc, TransCanada Corp and Enbridge Inc.

While aboriginal groups have long opposed oil sands development, the treaty signals a more coordinated approach to

fight proposals.

Among the treaty's signatories is the Standing Rock Sioux tribe who opposes the Dakota pipeline.

"What this treaty means is that from Quebec, we will work with allies in (British Columbia) to make sure that the Kinder Morgan pipeline does not pass," Kanesatake Grand Chief Serge Simon said in the statement.

"And we will also work with our tribal allies in Minnesota as they take on Enbridge's Line 3 expansion, and we know they'll help us do the same against Energy East," he said, referring to TransCanada's plan to carry 1.1 million barrels of crude per day from Alberta to Canada's East Coast.

The statement did not specify what actions the groups would take to stop development.

The Canadian Energy Pipeline Association, whose members include the targeted companies, said in a statement that the industry would listen to aboriginal concerns.

"The fact remains there is a critical need for pipelines in Canada," the association said, noting that they are the safest and most environmentally friendly way to move oil and gas.

Canada is assessing oil pipeline proposals as the country's energy-rich province Alberta reels from a crash in prices, partly due to insufficient means of moving oil to lucrative international markets.