Greenland is not for sale, Danish Prime Minister Mette Fredriksen said on Monday, after U.S. Secretary of State Marco Rubio said last week that President Donald Trump's interest in acquiring the island was "not a joke".

Denmark's prime minister reiterates 'Greenland is not for sale':: Brussels, Belgium:::: Mette Fredriksen, Danish Prime Minister "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,

The Ballistic Missile Early Warning System in Greenland, seen here in 2014, is one of three such installations that keep an eye out for long-range missiles leaving Russia. President-elect Donald Trump has said that the United States must take possession of Greenland for national security reasons.