The move, while expected, is still significant because it is only the third time that the current U.S. president has opted to shoot down a bill that Congress has signed off on.
"I am returning herewith without my approval … the Keystone XL Pipeline Approval Act," the president said in a letter to the U.S. Senate notifying them of the veto. "Through this bill, the United States Congress attempts to circumvent longstanding and proven processes for determining whether or not building and operating a cross-border pipeline serves the national interest."
But the move doesn't signal the end for the pipeline, which would carry oil from Canada to refineries in the U.S. The regulatory process is in its final phase as the State Department has finished collecting input and is now preparing a recommendation to the president. Obama must then decide whether the project is in the U.S. national interest.
Under U.S. law, a presidential veto can be offset if a bill gets two-thirds majority in either chamber of Congress – the Senate or the House of Representatives.
Republicans were quick to suggest Tuesday that they would try and do just that, bringing forward new legislation that would give approval to the 1,900-kilometre pipeline that would bring 800,000 barrels of Alberta crude oil every day to refineries on the U.S. Gulf Coast.
"We are not going to give up in our efforts to get this pipeline built — not even close," Speaker of the House of Representatives John Boehner said. "We pledged to make the people's priorities our priorities, and we will keep working every day to deliver on that commitment."
For its part, TransCanada — the Calgary-based company that wants to build and operate the pipeline — was quick to say it stands by the project, and looks forward to working with lawmakers to see it completed. "As we have done throughout the permitting process, TransCanada will keep working in good faith with the U.S. Department of State and other federal agencies to address any outstanding concerns with regard to Keystone XL," CEO Russ Girling said.
"Keystone XL is in the national interest of the United States and should be approved and constructed."