U.S. President Barack Obama has promised to show global leadership on climate change, a vow that could have a major impact on Canada’s oil exports to its largest customer as well as this country’s own climate debate.

The Harper government is lobbying heavily to have President Obama approve the Keystone XL pipeline that would carry 830,000 barrels per day of oil-sands bitumen to the vast refining complex on the U.S. Gulf and would ease the delivery bottlenecks that have driven down Canadian crude prices.

Opponents have mounted a well-organized, celebrity-studded campaign against the pipeline, arguing it would increase U.S. dependency on the oil sands, which they describe as the world’s dirtiest oil.

In his inaugural speech Monday, Mr. Obama highlighted climate change as a priority in his second term, though he will act without the support of Congress where the Republicans control the House of Representatives.