Donald Trump has declared that America must "own" Greenland to stop Russia and China gaining control of it.
"Countries have to have ownership and you defend ownership, you don't defend leases and we'll have to defend Greenland," Mr Trump told reporters on Friday.
And in a chilling ultimatum, the President warned the acquisition would happen "the easy way" or "the hard way".
His administration has considered purchasing the semi-autonomous Danish territory but has not ruled out a full annexation.
Mr Trump also claimed Greenland was "covered with Russian and Chinese ships all over the place".
"I love the people of China. I love the people of Russia," he said. "But I don't want them as a neighbour in Greenland, not going to happen."
"And by the way, Nato's got to understand that," Mr Trump added.
Denmark and Greenland have both firmly said the territory is not for sale.
Nato allies including major European nations and Canada have rallied behind Copenhagen this week, while Danish officials have warned that military action would effectively destroy the alliance.
"Only Denmark and Greenland can decide on matters concerning their relations," seven European nations said in a joint statement.
Mr Trump claimed Greenland was 'covered with Russian and Chinese ships all over the place'
|GETTY
The seven all said they were committed to Arctic security but insisted this must be achieved "collectively" with partners including the US.
They also called for "upholding the principles of the UN Charter, including sovereignty, territorial integrity and the inviolability of borders".
Greenland's position between North America and the Arctic makes it strategically valuable for missile early warning systems and maritime surveillance.
It straddles a number of vital northern shipping routes, and forms one edge of the "GIUK" gap, a strategic stretch of ocean between the UK, Iceland and Greenland which can be used to stop Russian vessels.
GREENLAND IN THE FIRING LINE - READ MORE:
PICTURED: A Danish Navy vessel sails off the coast of Greenland. Both the Scandinavian nation and the Arctic territory have firmly said the latter is not for sale
|GETTY
Greenland straddles a number of vital northern shipping routes
| GB NEWSThe territory also holds significant natural resources including rare earth minerals, uranium and iron.
The US already maintains over 100 military personnel at its Pituffik base on Greenland's northwest coast.
This facility has been operational since the Second World War.
Current agreements with Denmark permit the US to house unlimited troops in Greenland - but Mr Trump insisted that lease arrangements were insufficient.
"Countries can't make nine-year deals or even 100-year deals," he said, adding that America instead had to own it.
PICTURED: JD Vance and Second Lady Usha Vance tour the US military's Pituffik Space Base in Greenland
|REUTERS
But Britain has firmly ruled out allowing US forces to use its military bases for any operation against Greenland.
Defence Secretary John Healey was asked whether UK bases, personnel or equipment could support an extraordinary American takeover.
"There's no question of that," he told ITV News during a visit to Kyiv on Friday.
"Greenland and Denmark are part of Nato. We and the US are part of that alliance with treaty obligations," he reiterated.
"And so far as the UK's support for any nation with any military action, we will do so if the purpose is correct and if the legal basis is sound."
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