“I will never support the idea of fighting allies. But of course, if the US puts tough terms on Europe, we need a collective and robust response,” Danish Prime Minister Mette Frederiksen told reporters in Brussels as EU leaders gathered for defence talks.

Greenland, home to a large US military base, is an autonomous territory of Denmark, a long time US ally.

Last month, Trump left open the possibility that the American military might be used to secure Greenland, as well as the Panama Canal.

“We need Greenland for national security purposes,” he said.

Frederiksen said she has “great support” from her EU partners on the fact “that everybody has to respect the sovereignty of all national states in the world, and that Greenland is today a part of the Kingdom of Denmark. It’s part of our territory and it’s not for sale.”

She acknowledged US concerns about security in the Arctic Region, where Russia and China have been increasingly active.

“I totally agree with the Americans that the High North, that the Arctic region is becoming more and more important when we are talking about defence and security and deterrence,” Frederiksen said, adding that the US and Denmark could have “stronger footprints” in Greenland, in security terms.

“They are already there and they can have more possibilities,” she said, underlining that Denmark itself can also “scale up” its security presence.

“If this is about securing our part of the world, we can find a way forward,” Frederiksen said.

Last week, her government announced a roughly 14.6 billion kroner ($AUD3.25 billion) agreement with parties including the governments of Greenland and the Faeroe Islands to “improve capabilities for surveillance and maintaining sovereignty in the region.”

It would include three new Arctic naval vessels, two additional long-range surveillance drones and satellite capacity, the Defence Ministry in Copenhagen said.

Frederiksen’s remarks came as EU leaders met for defence talks but with no clear sign yet from Trump about how he intends to try to end Russia’s war on Ukraine.

The Europeans fear that any attempt to pull together a quick deal would not be favourable to Ukraine.

UK Prime Minister Keir Starmer and NATO Secretary-General Mark Rutte were set to join the bloc’s 27 leaders at a self-styled “retreat” at Egmont Place in the Belgian capital.

The summit agenda focuses on EU-US cooperation, military spending and ramping up Europe’s defense industry.

Trump already slapped duties on European steel and aluminium during his first term.

“We were listening carefully to those words, and of course we are preparing also on our side,” EU foreign policy chief Kaja Kallas said.

But, she underlined, “there are no winners in trade wars. If … the US starts a trade war, then the one laughing on the side is China. We are very interlinked.”