Eight nations targeted by new White House tariffs have hit back at President Donald Trump, accusing the U.S. of threatening to undermine transatlantic relationships and risking a "dangerous downward spiral."

Donald Trump has repeated his warnings of an imminent American takeover of Greenland in a late-night social media post. Trump, 79, is desperate to control Greenland, which is a semiautonomous territory of the Kingdom of Denmark.

The encroaching presence of China and Russia makes Greenland vital to U.S. security interests, Trump has said. Danish and other European officials have pointed out that Greenland is already covered by NATO's collective security pact.

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

In a floor speech, Thune’s predecessor as Republican leader, Sen. Mitch McConnell, warned that an attempt to seize Greenland would “shatter the trust of allies” and tarnish Trump’s legacy with a disastrous foreign policy decision.

Mr. Trump previously threatened to impose tariffs against countries that do not support his plans to acquire the territory.

What does Greenland have that Donald Trump wants? He said US needs control of the island for national security. What Denmark and Greenland leaders say