US President Donald Trump said he had agreed to a meeting of “various parties” over Greenland at the World Economic Forum in Davos, after holding a “very good” telephone call with Nato secretary-general Mark Rutte.

Jens-Frederik Nielsen, Greenland’s prime minister, said that an attack on the territory by the United States was “not likely” — but said that he could not rule one out.

The president fired off a series of posts well after midnight that included private messages from world leaders.

The heads of state of all 27 European Union nations will meet for an "extraordinary meeting" later this week, European council president Antonio Costa said on Sunday.

The Dow tumbled more than 600 points on Tuesday as investors assessed the impact of Trump's intensifying push to take control of Greenland.

The "Sell America" trade compelled investors to dump U.S. stocks and bonds, while gold and silver, both safe haven assets, hit fresh highs.

There were grave warnings from European leaders and expletives from California Gov. Gavin Newsom on Tuesday as leaders at the World Economic Forum grappled with the Greenland crisis and heightened concerns over global trade.

One Copenhagen clothing store's tongue-in-cheek take on U.S. President Donald Trump's red baseball caps has become an unlikely symbol of Danish solidarity with Greenland, as protests mount over Trump's demands to buy the vast self-governing territory.

The organization Support Greenland is selling merchandise that benefits Greenlandic causes, like youth resources and sustainable tourism.

The president shared a private message from France's Emmanuel Macron, part of a flurry of activity as he added new fuel to his clash with Europe over the Arctic territory.

Mr Trump has described such a purchase as “the easy way”, while declining to rule out a harder approach. Americans are lukewarm about a purchase but are firmly opposed to using force. Just 9% of respondents approved of military intervention in Greenland; 72% were against it. Even among Republicans just 22% were in favour while 52% were opposed.