One of Donald Trump's most influential aides has said Greenland should become part of the US in order to protect NATO and the Arctic.

Asked in an interview with CNN to confirm the US would rule out the use of force to annex the semi-autonomous region of fellow NATO member Denmark, Stephen Miller said, nobody's going to fight the US over the future of Greenland.

On Sunday, Trump repeated his insistence that the US needs Greenland - to the consternation of Danish Prime Minister Mette Frederiksen who asserted that an attack by the US would spell the end of NATO.

Six European allies rallied to Denmark's support with a joint statement on Tuesday.

Greenland belongs to its people, and only Denmark and Greenland can decide on matters concerning their relations, read the statement by leaders from the UK, France, Germany, Italy, Poland, Spain, and Denmark.

In his CNN interview, Miller stated that it was the formal position of the US government that Greenland should be part of the US. He questioned Denmark's claims over Greenland, asking, By what right does Denmark assert control over Greenland? What is their basis of claiming Greenland as a colony of Denmark?

Miller emphasized that the US is the primary power of NATO, and for the US to secure the Arctic region and defend NATO interests, Greenland should be included as part of the US.

The controversy surrounding Greenland's future surfaced in connection with the US military intervention in Venezuela, where Trump suggested the US would run Venezuela after a military operation targeting its President Nicolás Maduro.

The Trump administration's move to appoint a special envoy to Greenland has sparked anger in Denmark.

Greenland, with a population of 57,000, has had extensive self-government since 1979. However, defense and foreign policy remain under Danish control, and while many Greenlanders favor eventual independence, there is significant opposition to the idea of becoming part of the US.