The letter reiterated Trump’s complaints about dairy quotas, fentanyl and the U.S. trade deficit, which is mostly fueled by American refineries’ thirst for Canadian oil. His social media post caused the Canadian dollar to immediately tumble, indicating the market wasn’t expecting this escalation.

President Donald Trump on Thursday threatened to unleash tariffs of 35% on imports from Canada starting on August 1 as he continued his attack on the US' neighbor to the north.

Trump previously applied 25% tariffs to non-USMCA goods and the new rate, announced in a letter to Canadian Prime Minister Mark Carney and posted on social media, would mean that number rises to 35%, the official said. The U.S. and Canada had been involved in talks to lower tariffs ahead of a self-imposed July 21 deadline.