Six NATO members have vowed to defend the sovereignty and territorial integrity of Denmark and Greenland, following threats by U.S. President Donald Trump to take over Greenland.

Greenland, with its vast mineral deposits and location north of the Arctic, is a semi-autonomous region of Denmark.

The Trump administration has designated Greenland as strategic for U.S. national security, and the White House said on Tuesday that the use of military force is an option, dubbing it an "important foreign policy goal".

In a joint statement, NATO members Denmark, Germany, France, Spain, Italy, the UK and Poland reiterated that Greenland belongs to its people.

"It is for Denmark and Greenland and them only to decide on matters concerning Denmark and Greenland," they said.

Danish Prime Minister Mette Frederiksen warned that a U.S. annexation of Greenland could lead to NATO's collapse, in light of one member choosing to attack another.

The U.S. already has a military base in Greenland as part of a defence agreement with Denmark, signed in 1951.

However, in recent years, Trump has shown heightened interest in the territory, claiming that Denmark is unable to govern it.