Denmark and Greenland insist that the mineral-rich island is not for sale, while President Trump has not ruled out taking it by military force even though Denmark is a NATO ally.

Denmark summoned the top U.S. diplomat in the country for an explanation following a Wall Street Journal report about the United States stepping up its intelligence gathering on Greenland, a semi-autonomous Danish territory coveted by President Donald Trump.

U.S. officials have ordered spy agencies to ramp up efforts to gather intelligence on Greenland, according to two sources with knowledge of the matter, in a sign President Donald Trump apparently remains focused on acquiring the island. The directive was first reported by The W all Street Journal .