Mr. Trump said the decision came in response to Ontario's move to impose a 25% surcharge on electricity exports to the U.S. Mr. Trump has already imposed a 25% tariff on nearly all imports from Canada, and declared a 25% tariff rate on all steel and aluminum imports from any foreign country.

European Commission President Ursula von der Leyen said as the United States is “applying tariffs worth 28 billion dollars, we are responding with countermeasures worth 26 billion euros,” or about $28 billion.