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 president said.

The leaders of Mexico and Canada - two of the US's largest trading partners - have responded to the US president's steep taxes on imports.

The president said oil "may or may not" be affected by his tariffs on the two countries, which are set to take effect on Saturday.

US President Donald Trump has said he will follow through with his threat to hit imports from Canada and Mexico with 25% border taxes, known as tariffs, on 1 February. But he added that a decision about whether this would include oil from those countries has not yet been made.