NATO chief Mark Rutte has warned Europe cannot defend itself without the United States, in the face of calls for the continent to stand on its own feet after tensions over Greenland.
U.S. President Donald Trump roiled the transatlantic alliance by threatening to seize the autonomous Danish territory, before backing off after talks with Rutte last week.
The diplomatic crisis gave fresh momentum to those advocating for Europe to take a tougher line against Trump and break its military reliance on Washington.
"If anyone thinks here again, that the European Union, or Europe as a whole, can defend itself without the U.S., keep on dreaming. You can't," Rutte told lawmakers at the European Parliament.
He said that EU countries would have to double defense spending from the 5 percent NATO target agreed last year to 10 percent and spend "billions and billions" on building nuclear arms.
"You would lose the ultimate guarantor of our freedom, which is the U.S. nuclear umbrella," the former Dutch prime minister said. "So hey, good luck."
Rutte insisted that US commitment to NATO's Article Five mutual defense clause remained "total," but that the United States expected European countries to keep spending more on their militaries.
"They need a secure Euro-Atlantic, and they also need a secure Europe. So the U.S. has every interest in NATO," he said.
The NATO head also appeared to knock back a suggestion floated by the EU's defense commissioner Andrius Kubilius earlier this month for a possible European defense force that could replace U.S. troops on the continent.
"It will make things more complicated. I think [Russian President Vladimir] Putin will love it. So think again," Rutte said.
