Canadian Prime Minister Stephen Harper carried climate commitments with him when he visited Washington earlier this month.
Harper's government has lobbied in support of TransCanada's plans to build the cross-border Keystone XL pipeline to carry Canadian tar sands oil to southern U.S. refineries on the Gulf of Mexico.
Becky Bond, political director at the environmental advocacy group CREDO, said the pipeline would send tar sands oil, a grade viewed as more carbon polluting than other types of crude, through the United States.
"The health of our climate, and landowners from Texas on up to Nebraska, will pay the price for TransCanada's greed if President Obama doesn't act swiftly and reject Keystone XL," she said in a statement published Tuesday.
Obama said he'd weigh the project against its environmental footprint. A U.S. State Department review said some of the environmental effects of tar sands development would be prevalent with or without the pipeline.
"Plain and simple, TransCanada's Keystone XL pipeline is not in our country's interest," Amanda Starbuck, energy and finance director for Rainforest Action Network, said.
RAN said more than a dozen activists were arrested at TransCanada's headquarters in Houston during a recent rally in opposition of the pipeline.