OAKLAND, Calif. - An international coalition of environmental and Native American groups strongly opposed Thursday's U.S. State Department decision to issue a permit for a pipeline to carry the dirtiest oil on earth from Canada to the U.S. and vowed to challenge it in court.

"The State Department has rubber-stamped a project that will mean more air, water and global warming pollution, particularly in the communities near refineries that will process this dirty oil," said Earthjustice attorney Sarah Burt. "The project's environmental review fails to show how construction of the Alberta Clipper is in the national interest. We will go to court to make sure that all the impacts of this pipeline are considered."

The groups-Earthjustice, Indigenous Environmental Network, Minnesota Center for Environmental Advocacy and Sierra Club-pointed out that this decision contradicts President Obama's promise to cut global warming pollution and America's addiction to oil while investing in a clean energy future.

The State Department's decision would allow construction of Enbridge Energy's Alberta Clipper pipeline across northern Minnesota to Superior, Wis. and the Southern Lights pipeline to carry hazardous liquids back to Canada.

Tar sands development in Alberta is creating an environmental catastrophe, with toxic tailings ponds so large they can be seen from space and plans to strip away the forests and peat lands in an area the size of Florida. In addition, greenhouse gas emissions from tar sands production are three times that of conventional crude oil and it contains 11 times more sulfur and nickel, six times more nitrogen and five times more lead than conventional oil. These toxins are released into the U.S. air and water when the crude oil is processed into fuels by refineries.

"The tar sands pipeline connects U.S. refiners and consumers with the dirtiest, most carbon-intensive crude oil on earth," said Kevin Reuther, Minnesota Center for Environmental Advocacy's legal director. "Tar sands crude is causing massive environmental degradation in Canada and results in significantly more greenhouse gas emissions. This is the absolute wrong step to take if we want to create a greener energy future."

Secretary of State Hillary Clinton needed to find that allowing the pipeline to be built across the U.S.-Canadian border would be in the national interest of the United States. In fact, these two pipelines will hurt the United States.

"Importing dirty tar sands oil is not in our national interest," said Sierra Club executive director Carl Pope. "At a time when concern is growing about the national security threat posed by global warming, it doesn't make sense to open our gates to one of the dirtiest fuels on earth. This pipeline will lock America into a dirty energy infrastructure for years to come. This is exactly the kind of project the State Department should be protecting us from."

Many of the groups involved also have appealed the U.S. Forest Service over its willingness to allow the pipeline to traverse parts of the Chippewa National Forest in Minnesota. In addition, a group of tribal members have apparently gathered enough signatures on a petition to hold a referendum on the Leech Lake tribal council's agreement to allow the line through tribal land.