After a protracted battle with loud and fierce opposition coming from First Nations and environmental groups, public support in Canada is on the decline for the Keystone XL tar sands pipeline, according to a new survey (pdf) published Wednesday.

The study, conducted by the Ottawa-based Nanos Research Group, compares public opinion data from April 2013 to December 2013.

During that period, the number of Canadians who oppose or somewhat oppose the pipeline grew from 27.1 to 40.4 percent.

Further, 51.6 percent support or somewhat support approval of the project, compared to 67.5 percent who supported or somewhat supported approval in April.

"The poll adds to evidence that a push by environmental groups, aboriginal activists and celebrities such as musician Neil Young opposed to big oil projects may be affecting public opinion," wrote Bloomberg News, following release of the survey.

As opposition grows, all eyes remain on President Obama who, following the upcoming release of the U.S. State Department's final environmental assessment of the pipeline, is expected to make a determination on whether to greenlight the project.

Transcanada's proposed Keystone XL pipeline has galvanized both indigenous and environmental groups, who say the project will open up access to the "dirtiest fuel on the planet," the Alberta tar sands, by transporting the crude from Canada's oil fields to ports on the Gulf of Mexico.

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