Canadian Prime Minister Justin Trudeau is unwilling to lift Canada’s retaliatory tariffs on the United States if President Donald Trump leaves any U.S. tariffs on Canada, a senior government official told The Associated Press on Wednesday.

Prime Minister Justin Trudeau of Canada warned that the Trump administration’s tariffs were leading to a trade war. Mexico’s leader vowed to impose countermeasures on Sunday.

Canadian Prime Minister Justin Trudeau said he wouldn’t allow President Trump’s tariff decision to “go unanswered,” and set in motion the imposition of retaliatory tariffs targeting about $100 billion of U.