President-elect Donald Trump on Saturday threatened 100% tariffs against a bloc of nine nations if they act to undermine the U.S. dollar. His threat was directed at countries in the so-called BRIC 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.

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.