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".

Greenland is a self-ruling territory in the Danish kingdom, which means policymakers in Nuuk control most domestic issues. Denmark, which oversees defense and security policy on the mineral-rich Arctic island, is injecting 14.6 billion kroner ($2 billion) to ramp up defenses.

The US could be allowed to step up its military presence in Greenland, the prime minister of Denmark has said.

President Trump reportedly held a “fiery” call with Denmark’s Prime Minister Mette Frederiksen over the president’s insistence that U.S. control of Greenland is necessary for American national

At the end of the interview, Qarsoq Høegh-Dam, a top official with the Naleraq party and an adviser to Olsen, popped in to say hello. Høegh-Dam is a gregarious politico, of a familiar sort you often find in insular government towns. He said he was trying to organize a “watch party” for Trump’s inauguration.

Denmark is ready to allow the US to boost its presence in Greenland, Danish Prime Minister Mette Frederiksen said as she seeks to curb an escalating diplomatic crisis with the Trump administration over the world’s largest island.