US President Donald Trump is heading to Davos for a showdown with European leaders as his bid to seize Greenland threatens to tear the transatlantic alliance apart. The US leader brutally mocked the Europeans a day before heading to the World Economic Forum, where he will star in a drama over the fate of the autonomous Danish territory. But leaders in the Swiss ski resort have closed ranks against Trump's aggressive America First stance, with French President Emmanuel Macron vowing to stand up against "bullies" and the EU promising an "unflinching" response.