Belgium’s defense minister called on NATO to launch a security operation in the Arctic, urging transatlantic unity amid growing European ‍unease about U.S. President Donald Trump’s push to take control of Greenland.

“We have to ‌collaborate, work together and ‍show strength and unity,” Theo Francken said in a phone interview, adding that there is a need for “a NATO operation in the high north”.

Trump said on Friday that the U.S. needs to own Greenland to prevent Russia or China from occupying it in the future.

European officials have been discussing ways to ease U.S. concerns about security ⁠around Greenland, an autonomous territory of the Kingdom of Denmark.

Francken suggested NATO’s Baltic Sentry and Eastern Sentry operations, which combine forces from different countries with drones, sensors and other technology to monitor land and sea, as possible models for an “Arctic Sentry”.

He acknowledged Greenland’s strategic importance ‌but said “I think that we need to sort this out like friends and allies, like we always do”.

A NATO spokesperson said on Friday that alliance chief Mark Rutte ‍spoke with U.S. Secretary of State Marco Rubio about the importance of the ‍Arctic for shared ‍security and how NATO is working ⁠to enhance its capabilities ‍in the high north.

Denmark and Greenland’s leaders have said that the Arctic island could not be annexed and international security did not justify such a move.

The ⁠U.S. already has ‌a military presence on the island under a 1951 agreement.