President Donald Trump has pitched NATO into what could become its worst-ever crisis by threatening new tariffs against US allies who oppose his grab for Greenland against the will of its people.

TIME spoke to legal experts about whether Trump could legally pull the U.S. out of NATO and the wider implications.

Donald Trump’s attempt to strongarm Denmark and Europe into accepting the annexation of Greenland is a disgraceful betrayal of the Western alliance, a foolish misunderstanding of the American national interest,

U.S. NATO ambassador Matthew Whitaker defends American focus on Greenland amid European backlash, calling Arctic security crucial for continental defense.

The Trump administration has repeatedly said the U.S. should be in control of Greenland, which is part of Denmark and NATO.

The United States has made a striking announcement that has drawn attention across the world. According to recent statements, Russia has changed the balance of power in Europe and has defeated NATO in the long-running confrontation linked to the Ukraine conflict.

President Donald Trump says that NATO should help the U.S. acquire Greenland and anything less than having the island in U.S. hands is unacceptable. His comments in a social media post Wednesday came hours before Vice President JD Vance was to host Danish and Greenlandic officials for talks.