OTTAWA (Reuters) - Canada could potentially use oil and gas exports as a lever in negotiations if U.S. tariffs on Canadian imports escalate, Foreign Minister Melanie Joly told a Toronto business audience on Wednesday.

Canada is vowing to impose tariffs on C$155 billion worth of U.S. imports but has so far not suggested it would reduce exports of commodities to the United States. Canada exports about 4 million barrels per day of oil to the United States, approximately 90% of its total crude exports.

"Of course, there's oil and gas. We haven't put that on the table yet, guys, we kept that in our game, in our cards, as cards that we could potentially play if this would escalate, and the U.S. knows that," Joly said.

Alberta, Canada's main energy-exporting province, says it would never accept the idea of reducing energy exports to the United States.