CALGARY (Reuters) - Tariffs on Canadian oil would need to be in place for years before significantly altering the amount of crude the U.S. imports from its northern neighbour, the CEO of Canadian pipeline company Enbridge Inc. ( ENB ) said Tuesday.

Greg Ebel said the energy systems of the two countries are too integrated and there is no easy way for the U.S. to replace the approximately 4 million barrels per day of Canadian oil it imports.