The US-Canada trade relationship deteriorated sharply in late August 2026 after talks collapsed between August 22 and 25. Commerce Secretary Howard Lutnick accused Canada of introducing politically driven demands at the eleventh hour, including tariff relief for medium- and heavy-duty trucks, aluminum carve-outs and protection for its dairy supply management system. The US imposed new tariffs on roughly $20 billion of Canadian goods, and Canadian Prime Minister Mark Carney promised dollar-for-dollar retaliation, raising the prospect of a trade war between each country’s largest trading partner. Ottawa disputed Washington’s account, saying the US had unexpectedly shifted its position and that divisions among American negotiators had undermined the talks. The dispute puts integrated automotive, steel and aluminum supply chains under pressure and adds cost uncertainty for manufacturers, suppliers and exporters.