US President Donald Trump's pursuit of Greenland is part of the "America First" agenda to dominate the Western Hemisphere, experts say.
The Trump administration has signalled more than once its intent to take over the Arctic island, citing its importance to US national security.
"It's vital to deter our adversaries in the Arctic region. The ?president and his team are discussing a range of options to pursue this important ?foreign policy goal," the White House said in a statement issued on Wednesday.
"Of course, utilising the ?US military is ?always an option at the commander-in-chief's disposal."
After the US seizure of Venezuelan President Nicolás Maduro, Mr Trump repeated statements from as far back as his first term about the importance of Greenland to the US.
The military operation in Venezuela has reignited fears about Mr Trump's designs on the autonomous Danish territory.
Danish Prime Minister Mette Frederiksen warned that an invasion would end the decades-old North Atlantic Treaty Organisation (NATO) alliance.
But what makes territory so valuable to the US?
Why is Greenland strategically important?
Greenland, home to about 57,000 people, is in one of the most strategically important regions in the world for global trade and security.
Described as the world's largest island that is not a continent, it sits between the Atlantic and Arctic oceans, and a 1.7-million-square-kilometre ice sheet covers about 80 per cent of its territory.
University of Sydney's Dr Stuart Rollo, whose research focuses on the US-China relationship and imperial history, said the region's significance had grown in part as a result of ice melts making it easier to travel through Arctic waters between Europe, Russia and North America.
"Greenland has, since the Cold War, been used as a military outpost for the United States," Dr Rollo said.
"To both monitor the Russian military and also as a fuelling station for strategic bombers should they be used against Russia, and a base for missile defence against a potential Russian nuclear attack."
The reason superpowers such as the US, Russia and China are interested in Greenland is simple — geography, says Dr Elizabeth Buchanan, from the Australian Strategic Policy Institute.
Dr Buchanan, whose research focuses on polar strategy, said the new trade routes opening between Asia and Europe as the Arctic ice melts meant the global trade ecosystem was heading north.
It would make trade cheaper and quicker for both suppliers and consumers, she said.
"This makes Greenland a physical choke point at one end of the new global shipping highway," Dr Buchanan said.
"To ensure free-flowing goods and limit possible coercion, the US, and actually Europe too, want to ensure its competitors or adversaries are not entrenched."
Dr Rollo said China also viewed the region as important.
"A big strategic risk for China is that the US dominates maritime trade points around the world," he said.
"So the US can interdict shipping at the Straits of Malacca, in the Middle East, at the Panama Canal, and this could cut off China from global commerce.
"A safe passage through the Arctic, which would run mostly through from China up past Russian territory to markets in Europe, would be a lifeline for China should a conflict occur with the United States."
Greenland's untapped rare earths
Rare earths are a group of 17 elements used in items ranging from smartphones to missile systems.
The Trump administration has repeatedly stressed the significance of rare earths to combat China's dominance.
China accounts for about 70 per cent of rare earth mining, 90 per cent of separation and processing, according to the Centre for Strategic and International Studies.
Australian National University's John Mavrogenes, a professor of economic geology, said there were three major rare earth mines in the world.
These include Bayan Obo in China, Mountain Pass in the US, and Mount Weld in Western Australia.
US Geological Survey estimates Greenland has 1.5 million metric tonnes of rare earth reserves, which are largely untapped.
Professor Mavrogenes was unsure if mining Greenland's rare earth reserves was viable.
"So people like to say these are the biggest deposits in the world," he said.
"[But] if you calculate the percentage of rare earths in the rocks and the volume of these rocks, they could potentially be the largest reservoir on Earth.
"But they're also extremely low grade."
Professor Mavrogenes said the hype about Greenland's rare earths was not well thought through.
Existing mines in places such as the US, China and Australia had much higher grades of rare earths in comparison.
"Bayan Obo [in China] that's about 5, maybe 6 per cent rare earth. The one in California, Mountain Pass, is about 8 to 9 per cent rare earth," he said.
"These things in Greenland are less than 1 per cent … which means you need to move a hell of a lot of rock to get it out.
"Secondly, they are within minerals that we're not used to dealing with."
Why is Greenland so important to the US?
In December, the US released its national security strategy with a major focus on so-called hemispheric defence.
Dr Buchanan said Greenland represented the heart of the US's "hemispheric defence".
"The Arctic is the 'roof' of the Western Hemisphere. As is the Antarctic, the 'floor'," she said.
"The polar regions will find themselves at the near-top of a re-prioritised US interests list."
The national security strategy referenced a 200-year-old US foreign policy, the Monroe Doctrine, which declared the Western Hemisphere as the US's sphere of influence.
"After years of neglect, the United States will reassert and enforce the Monroe Doctrine to restore American pre-eminence in the Western Hemisphere," the document reads.
"…We will deny non-Hemispheric competitors the ability to position forces or other threatening capabilities, or to own or control strategically vital assets, in our Hemisphere."
The document was proof of the major shift in US foreign policy since WWII, according to Dr Rollo.
He said, in the past, the US pursued a "global model of empire" where it formed military alliances with powers around the world.
"The United States enjoys hegemony in its own region; it's unchallenged there, but it prevents rivals like China from achieving that position in their regions," he said.
"So the US wants hegemony in the Western Hemisphere, and it wants to deny China hegemony in Asia, and that is based around a network of alliances."
Dr Rollo pointed to the recent military action in Venezuela, where China is a major investor and importer of the South American nation's oil reserves.
"This was seen as a potential problem for the US, particularly in the future if it should be in conflict with China," he said.
"They don't want a sort of point of leverage and base of operations for China in their own hemisphere.
"The main mission then is no longer global domination, but it's to keep the US as a sort of first among equals."
How have Denmark and other NATO allies responded?
European leaders released a joint statement following the White House's rhetoric about a potential sale or military action as it relates to Greenland
European leaders responded to the White House's latest rhetoric about acquiring Greenland.
A statement included leaders from France, Britain, Germany, Italy, Poland, Spain, and Denmark.
The leaders said security in the Arctic must be achieved collectively with NATO allies, including the United States.
"Greenland belongs to its people. It is for Denmark and Greenland, and them only, to decide on matters concerning Denmark and Greenland," the statement read.
"NATO has made clear that the Arctic region is a priority and European Allies are stepping up."
It followed strong comments from Denmark's Prime Minister Mette Frederiksen, who said any military aggression against a NATO country would see "everything stop".
"That is, including our NATO and thus the security that has been provided since the end of the Second World War," she said.
Dr Rollo said the US's interest in controlling Greenland came as it sought to reduce its commitments to Europe, and by extension, NATO.
"It already has a base in Greenland called the Pituffik Space Base. It would certainly seek to expand that," he said.
"It would also be denying dominance of that space to Russia. So it would be a big threat to the United States in terms of its control over global maritime routes if Europe, Russia, and China were all to get along at some point in the future.
"Whereas if they control Greenland, they've got that locked in, they don't have to rely on the NATO alliance or anything else."
