WASHINGTON - Gary Doer says he has one primary mission as he promotes TransCanada's proposed Keystone XL pipeline in the United States as the State Department contemplates a final decision on whether to give the green light to the controversial project.

"Our job is to make sure it's a fact-based decision, on merit," Canada's ambassador to the United States said in an wide-ranging interview with The Canadian Press this week.

"If we can keep the decision fact-based, that's our job -- to keep the facts on the table."

The pipeline's proponents, he added, are hoping politics don't come into play as U.S. President Barack Obama embarks on a re-election campaign that aims to vilify congressional Republicans.

Those very Republicans are almost overwhelmingly in favour of the pipeline, saying it will create much-needed jobs and help end American reliance on Middle Eastern oil. Energy Secretary Steven Chu weighed in last week, suggesting the project will likely be approved given the close relationship between Canada and the U.S.

Many environmentalists in Obama's liberal base, meantime, have threatened to stay home in 2012 if he approves Keystone, which will carry oilsands crude through six U.S. states to refineries on the Gulf Coast of Texas. Will the struggling president side with his base, or the Republicans he hopes to demonize?

"If it's political," Doer concedes, "you don't know which way that's going."

Throughout the debate in the U.S. about the oilsands and Keystone XL, Doer has frequently railed against the "frozen facts" being put forth by environmentalists, accusing them of spreading outdated information.

"We don't want people to purport, for example, that (oilsands production) uses this much water when it's way less now," he said from his sixth-floor suite at the Canadian embassy, the majestic Capitol building in full view just a couple of blocks away.

"There's been great progress made on the sustainability of the oilsands. When you look at water, water utilization has gone down dramatically, and it's also gone down below ethanol production. But can we stand on the status quo? No, we have to keep improving."

Doer made his comments just days after the end of a two-week civil disobedience campaign that resulted in more than 1,200 arrests outside the White House. The group that organized the protest, Tar Sands Action, is vowing "phase two" of their efforts to convince Obama to block the $7 billion Keystone XL.

"Details are being hammered out now, but suffice to say: we have our work cut out for us," reads a brief on tarsandsaction.org. "Start by circling October 7th on your calendar...This movement doesn't end here."

Canadian environmental activists will hold their own protests against the pipeline on Parliament Hill on Sept. 26.

Keystone XL cleared one hurdle recently, when the State Department released its final environmental analysis of the pipeline and determined there would be no significant impact on the six states it traverses.

U.S. environmentalists, who have found a lightning rod in pipeline opposition in the wake of last year's failed federal climate change legislation, regard the State assessment as a sign that the Obama administration is poised to rubberstamp the project.

A final decision by the administration is expected by the end of the year. Republicans in the House of Representatives have tried to speed up the process, passing a resolution this summer that aimed to push Obama into making a decision as soon as possible.

Doer points out that "a number of Democrats" also supported the resolution.

"It's not just Republicans," he said.

"And if you look at the trade unions, the pipefitters -- they don't get many jobs building refineries in Algeria. They get jobs with refineries in Canada and the United States. .... My God, there's 20,000 direct construction jobs and thousands of other of indirect jobs created by the pipeline."

Doer had words of praise for Obama, whose approval ratings are sinking among supporters as well as foes.

Obama hasn't been duly commended by environmentalists, Doer said, for his achievements on vehicle emissions standards.

In July, the Obama administration and 13 automakers announced plans to improve efficiency standards for passenger cars and light trucks that will amount to significant reductions in their greenhouse gas emissions. Heavy trucks are next, Doer says.

The biggest source of carbon emissions in North America, Doer added, are from automobiles, so the barely noticed announcement -- made during the chaos of the debt ceiling debate -- is a significant one.

"The biggest way to deal with fossil fuels is to actually consume less through energy efficiency; that would be my humble opinion," Doer said.

"In all fairness to the president, I don't think he's getting enough credit for taking a very, very strong stand on vehicle emissions which are going to be very important for cleaner air in the United States and Canada .... the vehicle emission standards should not be sneezed at."