"Planning is underway for a NATO enhanced vigilance activity, named Arctic Sentry," said Martin O'Donnell, a spokesman for NATO's Supreme Headquarters Allied Powers Europe.

"The activity will even further strengthen NATO's posture in the Arctic and High North," he added, without providing further details.

Trump's threats against Greenland last month plunged the transatlantic alliance into its deepest crisis in years.

The unpredictable US leader backed off his desire to take control of Denmark's autonomous Arctic territory after saying he had struck a "framework" deal with NATO chief Mark Rutte to ensure greater American influence.

NATO said it would take steps to boost its presence in the Arctic after Trump used the alleged threat of Russia and China to justify his designs on Greenland.

Meanwhile Denmark and Greenland have kicked off talks with the United States over the territory and are expected to renegotiate a 1951 treaty governing American troop deployments on the island.

Danish Prime Minister Mette Frederiksen has said that NATO countries back having a "permanent presence" in the Arctic, including around Greenland, as part of efforts to step up security.