Denmark’s foreign minister said Monday he was “deeply upset” by US President Donald Trump’s appointment of a special envoy to Greenland who declared that he wished to see the island become part of the United States.

U.S. President Donald Trump on Monday said the United States needs to have Greenland, not for critical minerals but for national security.

The dispute comes as strategic competition in the Arctic grows, with melting ice opening new shipping routes and increasing access to valuable mineral resources.