The president-elect’s opening salvo in trade and border talks with the United States’ neighbors is casting a harsh light on the North American alliance.

Trump said Monday on Truth Social that one of his first executive orders would be to hit Mexico and Canada with a blanket 25% tariff. Mexico and Canada are the second and third top suppliers of goods to the U.S., according to the Office of the U.S. Trade Representative. The U.S. imports the most goods from China.

Prime Minister Justin Trudeau said that if President-elect Donald Trump follows through on this threat to impose tariffs on Canadian products, he would be raising prices and hurting American businesses.