Greek Prime Minister Kyriakos Mitsotakis said on Monday that any attempt to change the status quo of Greenland would be “catastrophic” and would amount to a direct challenge to NATO, marking a rare public rebuke of the Trump administration by a close U.S. partner.

“Greenland is NATO territory and I would say, any attempt to change this status-quo would be — I don’t hesitate to say that — catastrophic,” Mitsotakis said at an event in Athens late on Monday. He added that such a move “would constitute a direct challenge to NATO” and could become “the last straw in a difficult relationship that we’re now having with the United States.”

The comments stand out as an unusually direct intervention by the Greek leader, who has generally maintained a cautious tone toward Washington. Greece and the United States have strengthened their relationship in recent years, particularly through cooperation in the energy sector, as Washington has sought to deepen ties with Athens.