The 1,700-mile project is "unlikely to have a significant impact" on global warming, Canadian Natural Resources Minister Joe Oliver told reporters after Obama said he would approve the controversial pipeline only if it didn't "significantly" increase net greenhouse-gas emissions.
"I just think if you look at the facts and the science, we're comfortable the project will be approved," Oliver said.
He cited a 2,000-page U.S. State Department revised environmental impact statement from March that said "approval or denial of the proposed project [was] unlikely to have a substantial impact on the rate of development in the oil sands, or on the amount of heavy crude oil refined in the Gulf Coast area."
The statement had said if the pipeline were to increase the rate of development of the oil sands, also known as tar sands, it would increase global greenhouse gas emissions.
The State Department heads Washington's regulatory process on Keystone. The department is expected to issue its final report later this year. Obama will then make the final decision.
The $7 billion pipeline would carry upwards of 1 million barrels a day of synthetic crude oil and diluted asphalt-like petroleum extracted from Alberta, north of Montana, to refineries on the Texas and Louisiana Gulf Coast.
Obama spoke about the pipeline to a Georgetown University audience as part of a broader policy address on global warming.
"Allowing the Keystone pipeline to be built requires a finding that doing so would be in our nation's interest," he said.
"And our national interest will be served only if this project does not significantly exacerbate the problem of carbon pollution," Obama said to applause.
"The net effects of the pipeline's impact on our climate will be absolutely critical to determining whether this project is allowed to go forward," he said.
The climate factor cannot be ignored, he said. "It's relevant."
Oliver said Keystone -- which he called the most-studied pipeline "in the history of the world" -- would create jobs, boost the economies of both countries and increase Canadian and U.S. energy security.
The project was in the "national interests of both our countries," he said.
TransCanada Corp., the Calgary, Alberta, company seeking the permit to build the pipeline, also said the project easily met Obama's criteria.
"If Keystone XL is not built, it's clear that the oil will move to market by truck, rail and tanker, which will significantly add to global greenhouse-gas emissions to move the product," the company said in a statement.
The pipeline itself will "operate with virtually no emissions" and have a "limited impact" on the environment along its proposed route, the statement added.
Pipeline opponents interpreted Obama's remarks differently.
"With this promise to the American people to reject the pipeline if it will increase climate pollution, the president has taken a huge step toward rejecting Keystone XL, given that evidence has already shown it will increase [greenhouse-gas] emissions and have serious climate consequences," Rachel Wolf, spokeswoman for the anti-Keystone coalition All Risk, No Reward, said in remarks quoted by The Toronto Star.
"The Keystone pipeline is key to accelerate tar sands expansion plans, which would lead to more carbon pollution," added Greenpeace Canada spokesman Mike Hudema in a statement.
Canadian Prime Minister Stephen Harper has called Keystone approval so obvious it's a "no brainer."