Denmark sent private messages in recent days to President-elect Trump's team expressing willingness to discuss boosting security in Greenland or increasing the U.S. military presence on the island, two sources with knowledge of the issue tell Axios. Trump's refusal to rule out military force to take control of Greenland was effectively a threat to invade a longstanding NATO ally. Those comments caught Copenhagen and many other European capitals off guard. Greenland (pop. 56,000) is largely autonomous, but Denmark maintains responsibility for defense. Trump has repeatedly declared that controlling Greenland — the world's largest island — is necessary for U.S. national security vis-a-vis Russia and China. His son Don Jr. visited Greenland this week bearing MAGA hats.

Climate change is opening up the Arctic for competition between superpowers, and could also make it easier to tap Greenland's mineral riches. The Danish government wants to convince Trump, including through the messages passed to his advisers this week, that his security concerns can be addressed without claiming Greenland for the U.S. One European diplomat told Axios that Denmark is widely seen as one of the closest allies of the U.S. within the EU, and no one could have imagined it would be the first country with which Trump would pick a fight. Danish Prime Minister Mette Frederiksen and her Greenlandic counterpart Múte Egede met on Friday in Copenhagen to discuss the situation. In a press conference after the meeting Frederiksen said she asked for a meeting with Trump. Egede said he is also ready to talk to the president-elect.

"Greenland is for the Greenlandic people. We do not want to be Danish, we do not want to be American. We want to be Greenlandic," Egede, an advocate for independence, said at the press conference. The sources said the Danish government wants to avoid a public clash with the new U.S. administration, and asked members of the Trump team for clarification regarding what exactly the president-elect meant in his comments earlier this week. In the messages passed to the Trump team, the Danish government made clear Greenland was not for sale but expressed readiness to discuss any other U.S. request regarding the island, the sources said. The U.S. already has a military base on Greenland and an agreement with Denmark dating to 1951 on defending the island, under which an increase of U.S. forces could easily be discussed. Danish officials have already said they are looking into further measures to increase investment in military infrastructure and capabilities in Greenland, in consultation with the Greenlandic government.

Greenland played a key role in NATO and U.S. defenses during the Cold War as part of an early warning system to detect Soviet submarines, or potentially missiles. With new sea lanes opening up as climate change reshapes the Arctic, Greenland's geography is becoming all the more important. But if Trump's real concern is security, there's no reason the U.S. couldn't simply increase its military presence and capabilities in Greenland under its alliance with Denmark, contends Malte Humpert, a founder and senior fellow at the Arctic Institute. Secretary of State Blinken downplayed Trump's comments and said there's no point wasting time on them. "It is not a good idea and it is not going to happen," Blinken said. But Trump's continued comments about this issue, and his son's visit, mean Danish and Greenlandic officials can't rule out the possibility that Trump is quite serious. The main question is whether Trump would be content to cut a deal with Denmark and declare victory, or whether his true mission is to become the first president in 80 years to gain new territory for the U.S.

The administration of President Harry Truman pitched a sale to Copenhagen in 1946, in a story told in documents contained in the National Archives and revealed in 1991 by The Associated Press. But the Truman administration did so under Cold War secrecy and no one learned about it for decades. There was no open bid and rejection as with Trump's attempt.

A dangerous chill was settling between the United States and the Soviet Union following the conclusion of war in Europe. Truman and his Soviet counterparts were arranging pieces on a strategic chessboard for what would become the Cold War. That's why, according to the AP's account of the National Archives papers, Truman's advisers prized the geographic advantage Greenland could afford to defend against Soviet strategic bombers that might fly over the Arctic Circle toward targets in North America. The United States opened negotiations with Denmark about using Greenland, and at one point, the American side proposed buying the island outright for $100 million in gold and the rights to a patch of Alaskan oil.

All this took place in confidence but even then — as now — the idea shocked the Danes. Here's how the AP's W. Dale Nelson described the National Archive documents' account of the exchange: Secretary of State James Byrnes made the offer to visiting Danish Foreign Minister Gustav Rasmussen in New York on Dec. 14, 1946, according to a telegram from Byrnes to the U.S. Legation in Copenhagen. After discussing other security arrangements for Greenland, Byrnes said he told Rasmussen that perhaps an outright sale to the United States ″would be the most clean-cut and satisfactory.″ ″Our needs ... seemed to come as a shock to Rasmussen, but he did not reject my suggestions flatly and said that he would study a memorandum which I gave him,″ he said."