The United States and Canada have plunged into a trade war as Ottawa stands its ground in the face of President Donald Trump's latest tariffs, taking on the world's largest economy.

The trade war between the United States and Canada has heated up - amid the collapse of negotiations between the two countries.

Canada-US tariffs: Canadian Prime Minister Mark Carney says Canada was “attacked” and is “at war” with the US over trade as President Donald Trumps 50% tariffs trigger a fresh…