Denmark and Greenland are seeking a meeting with US Secretary of State Marco Rubio after the Trump administration doubled down on its intention to take over the strategic Arctic island.
Tensions escalated after the White House said on Tuesday that the "US military is always an option."
President Donald Trump has argued that the US needs to control the world's largest island to ensure its own security in the face of rising threats from China and Russia in the Arctic.
Danish Prime Minister Mette Frederiksen warned earlier this week that a US takeover of Greenland would amount to the end of NATO.
"The Nordics do not lightly make statements like this," Maria Martisiute, a defence analyst at the European Policy Centre think tank, said on Wednesday.
"But it is Trump, whose very bombastic language bordering on direct threats and intimidation, is threatening the fact to another ally by saying 'I will control or annex the territory.'"

The leaders of France, Germany, Italy, Poland, Spain and the United Kingdom joined Frederiksen in a statement on Tuesday reaffirming that the mineral-rich island "belongs to its people."
Their statement defended the sovereignty of Greenland, which is a self-governing territory of Denmark and part of NATO.
The US military operation in Venezuela last weekend has heightened fears across Europe and Trump and his advisers in recent days have reiterated a desire to take over the island, which guards the Arctic and North Atlantic approaches to North America.
"It's so strategic right now," Trump told reporters on Sunday.
Danish Foreign Minister Lars Løkke Rasmussen and his Greenland counterpart, Vivian Motzfeldt, have requested a meeting with Rubio in the near future, according to a statement posted Tuesday to Greenland's government website on Wednesday.
Previous requests for a sit-down were not successful, the statement said.
'This is America now'
Thomas Crosbie, an associate professor of military operations at the Royal Danish Defence College, said an American takeover would not improve upon Washington's current security strategy.
"The United States will gain no advantage if its flag is flying in Nuuk versus the Greenlandic flag," he said.
"There's no benefits to them because they already enjoy all of the advantages they want. If there's any specific security access that they want to improve American security, they'll be given it as a matter of course, as a trusted ally. So this has nothing to do with improving national security for the United States."

Denmark's parliament approved a bill last June to allow US military bases on Danish soil. It widened a previous military agreement, made in 2023 with the Biden administration, where US troops had broad access to Danish airbases.
Rasmussen, in a response to lawmakers’ questions, wrote over the summer that Denmark would be able to terminate the agreement if the US tries to annex all or part of Greenland.
But in the event of a military action, the US Department of Defence currently operates the remote Pituffik Space Base, in northwestern Greenland, and the troops there could be mobilised.
Crosbie said he believes the US would not seek to hurt the local population or engage with Danish troops.
"They don't need to bring any firepower. They don't to bring anybody," Crosbie said on Wednesday.
"They could just direct the military personnel currently there to drive to the centre of Nuuk and just say, 'This is America now,' right? And that would lead to the same response as if they flew in 500 or 1,000 people."
'Greenland is not for sale'
French Foreign Minister Jean-Noël Barrot said he spoke by phone with Rubio on Tuesday, who dismissed the idea of a Venezuela-style operation in Greenland.

"In the United States, there is massive support for the country belonging to NATO – a membership that, from one day to the next, would be compromised by…any form of aggressiveness toward another member of NATO," Barrot told France Inter radio on Wednesday.
Asked if he has a plan in case Trump does claim Greenland, Barrot said he would not engage in "fiction diplomacy."