The president urged his successor to reconsider his threats to impose sweeping tariffs on Canada and Mexico, warning they could undermine relations with two of the U.S.’s closest allies.

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.

Earlier this week, Trump said he would impose a 25% tariff on all goods from Mexico and Canada as soon as he takes office.