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 said 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 the leaders of the UK, France, Germany, Italy, Poland, Spain, and Denmark.