On a visit to Greenland a few months ago, Danish Prime Minister Mette Frederiksen warned the US that "you cannot annex another country".

Denmark's foreign minister said in a statement to the BBC that the government was "aware that foreign actors continue to show an interest in Greenland and its position in the Kingdom of Denmark".

"It is therefore not surprising if we experience outside attempts to influence the future of the Kingdom in the time ahead," he added.

Denmark is a member of Nato and the European Union and has long seen the US as one of its closest allies, and Danes have been shocked by Trump's determination to control its semi-autonomous territory. The US president said this year he would not rule out seizing it by force.