President Donald Trump said in an Oval Office signing ceremony Monday evening that his administration will impose 25% tariffs on Mexico and Canada on February 1, an extraordinary change in North American trade policy that could raise prices for American consumers.

Trump underscored his intention to use tariffs as a tool of international economic policy and an increasingly vital source of government revenue.

Americans buy $900 billion a year in food, cars, TVs, toys, appliances and other goods from Mexico and Canada. The cost of these products could rise if President Trump carries out his threat to apply 25% tariffs.