Allies including France and Germany are working closely on a plan on how to respond should the United States act on its threat to take over Greenland.

European leaders on Tuesday issued a joint statement to push back against U.S. President Donald Trump's renewed interest in Greenland.

Were Trump to make good on his ambition to bring Greenland under US control, would it mark not just an existential threat to Nato but also a major crisis for the EU?