The president’s trade assault, which makes no distinction between ally and adversary, is an assertion of U.S. dominance with significant risks.

Amid warnings of price increases, Canada moved quickly to retaliate, China said it had planned countermeasures, and Mexico said it would soon unveil its response.

Trump’s move to impose new tariffs has bewildered the United States’ closest allies and trading partners, who have vowed to respond with levies of their own.