President Donald Trump’s 50% tariffs on scores of Canadian imports kicked in Saturday. The new taxes will raise prices for American companies and consumers on about 5% of Canada’s annual exports to the U.S., roughly $20 billion in goods ranging from agricultural products to hockey sticks. Prime Minister Mark Carney quickly promised Saturday that Canada will impose retaliatory measures “dollar for dollar” starting Sept. 8.

Iran’s Foreign Ministry spokesperson warned on Monday that Tehran would respond harshly to expanded U.S. sanctions, after the new head of Iran’s top security body warned that Tehran will see any country’s support for new U.S. economic measures against the Islamic Republic as an “act of war.”