"Greenland is ours. We are not for sale and will never be for sale. We must not lose our long struggle for freedom," the island's Prime Minister Mute Egede said in a written comment.

Trump on Sunday announced that he had picked Ken Howery, a former envoy to Sweden, as his ambassador to Copenhagen, and commented on the status of Greenland, a semi-autonomous part of Denmark and host to a large U.S. Air Force base.

"For purposes of National Security and Freedom throughout the World, the United States of America feels that the ownership and control of Greenland is an absolute necessity," Trump wrote on Truth Social.

Trump, who takes office on Jan. 20, did not elaborate on the statement.

The Danish government was not immediately available for comment.

Greenland, with its Pituffik air base, is strategically important for the U.S. military and its ballistic missile early-warning system, since the shortest route from Europe to North America runs via the island.

During his previous term in office, Trump in 2019 expressed interest in buying Greenland, but the proposal was promptly rejected by Denmark as well as by the island's own authorities before any formal discussions could take place.

Danish Prime Minister Mette Frederiksen as the time labelled Trump's offer as "absurd", leading him to term her dismissal of the idea as "nasty" and to subsequently cancel a visit to Copenhagen.

Frederiksen remains in her role of Danish prime minister.

Since 2009 Greenland has held the right to declare independence from Denmark. The island of some 56,000 inhabitants, which relies on significant budget transfers from Copenhagen each year, has so far refrained from doing so.

Separately on Sunday, Trump threatened to reassert U.S. control over the Panama Canal, accusing Panama of charging excessive rates to use the Central American passage and drawing a sharp rebuke from Panamanian President Jose Raul Mulino.