Canadian Prime Minister Mark Carney told President Donald Trump Wednesday that his nation will retaliate against the United States with tariffs of its own if Trump presses forward with his promised levies – potentially escalating what is already developing into an ugly and damaging trade war.

Canada’s economic growth slowed down significantly last month, raising fresh concerns about the impact of Trump’s tariffs. On Friday, Trump said that he spoke with Carney and planned a meeting to negotiate a ‘new economic and security relationship’ after Canada’s upcoming election.