Danish Prime Minister Mette Frederiksen admitted on Tuesday that she was “annoyed” after US President Donald J. Trump abruptly announced that would cancel his upcoming official visit to Denmark after being told that Greenland – an autonomous region within the Kingdom of Denmark – was not for sale.

Following a 2008 self-government act, Greenland’s local government has a substantial say in the affairs of the region, a fact that Frederiksen underscored when she noted that Greenland’s leader, Kim Kielsen, flatly rejected Trump’s offer as “absurd” and that the world’s largest island – three-quarters of which is covered by the only permanent ice sheet outside Antarctica – and its 56,000 residents were “not for sale”.

According to Danish legal experts, Denmark could technically sell the island only after Greenlanders hold a referendum on whether they would agree to a sale and a transfer of their national identity.

Trump was scheduled to visit Denmark on 1 September 2 at the invitation of the country’s Queen Margrethe II. Frederiksen underscored that the visit would have been an opportunity to celebrate Denmark’s close relationship with the US, saying that the invitation remains open and adding, “The American president and the American people are and always will be welcome in Denmark.”

Frederiksen, who reiterated that she was surprised and deeply disappointed that Trump called off his visit reiterated her position that the US and Denmark need to further deepen their alliance as developments in the Arctic, including the militarisation of the region by Russia, called for further cooperation.

Trump, however, was less magnanimous in his response and lashed out at Frederiksen by saying she had been “nasty” after she rebuffed his idea of buying Greenland. Trump announced on his personal Twitter account on Tuesday evening that would no longer travel to Denmark because Frederiksen had refused to discuss the sale of Greenland, which had not originally been on the talking points agenda for the meeting.

Taking to Twitter to voice his displeasure, Trump expressed dismay at prime minister Frederiksen’s use of the word “absurd” saying she was foolish to reject such “a large real estate deal.” He later went on to sharply criticise Denmark – one of the largest contributors to counter-terror operations around the world as well as the US-led NATO missions in Iraq and Afghanistan – that it did not meet the 2% NATO defence spending threshold.

Denmark first allowed the US Air Force to establish a strategic radar base for its nuclear early warning system during the Cold War. The US’ Thule Air Base remains the US Armed Forces’ northernmost installation and central to NATO’s northern defence umbrella in the event of a nuclear strike launched over the North Pole.

Secretary of State Mike Pompeo spoke with Danish Foreign Minister Jeppe Kofod following Trump’s Tweets, which both later described as “constructive” and reaffirming for the close partnership between the two countries.

Greenland is rich in coal, zinc, copper, and iron ore and is rapidly becoming key to an ongoing struggle between the West, Russia, and China over the Arctic’s natural resources