Shawn Howard, a spokesman for pipeline planner Keystone XL, said the pipeline would move oil from Alberta to southern U.S. refineries with "almost no direct emissions."
Critics of Keystone XL said the heavier type of Canadian crude oil designated for the pipeline is more corrosive and more carbon intensive than other grades of crude oil. Obama, who needs to sign off on the cross-border pipeline, said he'd weigh the project against its environmental footprint.
The Natural Resources Defense Council said Harper's government is falling short of its efforts to curb emissions.
"Any credible plan to address Canada's climate emissions is incompatible with tar sands expansion," NRDC attorney Anthony Swift said in a statement Saturday.
Howard said Canada's track record on the environment was strong.
"Keystone XL will replace one source of heavy oil from places in the Middle East and Venezuela with another source of heavy oil -- resulting in virtually no global impact on emissions," he said.
Pregnant Mila Kunis wins 'Best Villain' at MTV Movie Awards
Pistorius testifies he didn't consciously pull trigger when he shot girlfriend