President Donald Trump published a letter to Prime Minister Mark Carney on Thursday, accusing Canada of having "financially retaliated" against the U.S.

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.