President Donald Trump has signed an order to impose stiff tariffs on imports from Mexico, Canada and China, drawing swift retaliation from the U.S.’s North American neighbors in an emerging trade war.

American importers will pay a new 25 percent tax on goods from Canada and Mexico and a 10 percent levy on products from China.

The White House said the president’s order includes a mechanism to escalate the rates if the countries retaliate, as they have threatened.