The cheap Canadian oil America craves is becoming a key bargaining chip in President Trump’s threatened trade war.

Trump pledged in his inaugural address that tariffs would be coming in a speech in which he promised a golden era for America. He later said Canada and Mexico could be hit with the tariffs as soon as Feb. 1, though he signed an executive order requesting a report coordinated by the Secretary of Commerce by April. 1.

The president said he planned to put tariffs on America’s neighbors on Feb. 1, as he signed an executive order mandating a sweeping review of U.S. trade policy.