A handout picture released by the BBC shows Britain's Prime Minister Keir Starmer speaking. AFP
"Well, I stand with her, and she's right about the future of Greenland," Starmer told reporters.
"Greenland and the Kingdom of Denmark are to decide the future of Greenland -- and only Greenland and the Kingdom of Denmark," he said.
Starmer's comments came after Danish Prime Minister Mette Frederiksen on Sunday told the US to stop "threatening its historical ally" following Trump's statements that he "absolutely" needed Greenland, which is Danish autonomous territory.
Washington's military attack on Venezuela has reignited fears about Greenland, the mineral-rich Arctic territory which Trump has repeatedly said he wants to annex.
"We need Greenland from the standpoint of national security, and Denmark is not going to be able to do it," he told reporters aboard Air Force One late on Sunday.
The island has untapped rare earth minerals and could be a vital player as the polar ice melts and new shipping routes emerge.
Greenland is also on the shortest route for missiles between Russia and the United States, and Washington already has a military base there.
"We'll worry about Greenland in about two months," continued Trump. "Let's talk about Greenland in 20 days."
Greenland Prime Minister Jens-Frederik Nielsen took to social media to tell the US leader: "That's enough now. No more pressure. No more insinuations. No more fantasies of annexation."
"We are open to dialogue," he said. "But this must happen through the proper channels and with respect for international law."
'China threat'
Trump rattled European leaders by attacking Caracas and abducting Venezuelan president Nicolas Maduro, who is now being detained in New York.
Trump has said the United States will "run" Venezuela indefinitely and tap its huge oil reserves.
The US leader has been similarly ramping up pressure on Greenland for months, saying in December that Russian and Chinese ships were "all over" the territory's coast.
The foreign ministry in Beijing hit back on Monday, urging Washington to "stop using the so-called China threat as an excuse to seek personal gain".
Aaja Chemnitz, an MP who represents Greenland in the Danish parliament, accused Trump of "spreading lies about Chinese and Russian warships".
"The people of Greenland should go into preparation mode," she told AFP, adding that Greenlanders needed to start taking Trump much more seriously.
On the streets of Copenhagen, locals expressed bewilderment at Trump's threats.
"I think it's a little crazy that he can say those things," said Frederik Olsen, 56.
"He has all the access he wants for the troops," said Christian Harpsoe, 46, adding: "I see no need. You cannot compare this to Venezuela."
'Disrespectful'
The controversy drew a slew of supporting statements from around Europe, with EU foreign policy spokesperson Anitta Hipper telling reporters the bloc was committed to defending the territorial integrity of its members.
France's foreign ministry spokesman Pascal Confavreux told local TV that "borders cannot be changed by force" and added that his country felt "solidarity" with Denmark.
The latest flare-up came after a weekend of high tension sparked on Saturday by former Trump aide Katie Miller, who posted online an image of Greenland in the colours of the US flag with the caption "SOON".
Nielsen labelled the post "disrespectful" and Frederiksen on Sunday called on Washington to stop "threatening its historical ally" and called US claims on Greenland "absurd".
Katie Miller is the wife of Trump adviser Stephen Miller, who is widely seen as the architect of many of Trump's policies, guiding the president's hard-line immigration policies and domestic agenda.
In response to Katie Miller's post, Denmark's ambassador to Washington, Jesper Moeller Soerensen, said his country was already working with Washington to boost security in the Arctic.
"We are close allies and should continue to work together as such," Soerensen wrote.
Short link: