Trump has said repeatedly he wants Canada to become the 51st state. It's a statement sometimes laughed off in the U.S., but viewed as deadly serious in Canada.

U.S. President Donald Trump on Tuesday ramped up the burgeoning trade war with Canada, vowing to double tariffs set to take effect within hours on all imported steel and aluminum products from America's northern neighbor to 50% - although he later said he would likely lower them after Canadian officials agreed to talks.