BRUSSELS (AP) — European Union foreign policy chief Kaja Kallas on Monday rejected calls for a Europe-wide army, warning that it could be “extremely dangerous” as the bloc considers ways to provide its own security after the United States warned that its priorities lie elsewhere.

Talk of a European army has resurfaced amid tensions within NATO over President Donald Trump’s threats to annex Greenland, the semiautonomous territory of NATO-ally Denmark.

“Those who say that we need a European army, maybe those people haven’t really thought this through practically,” Kallas said. “If you are already part of NATO then you can’t create a separate army.”

Kallas told a security conference in Norway that the most important military asset during a crisis “is the chain of command — who gives orders to whom.”

She added: “And if you have, like the European army and then you have the NATO (one), then, you know, the ball just falls between the chairs. And this is extremely, extremely dangerous.”

NATO’s military operations are overseen by a Supreme Allied Commander, who is always a top U.S. officer. The role is currently held by Airforce Lt. Gen. Alexus Grynkewich.

Norway’s Prime Minister Jonas Gahr Støre said: “NATO is there with the decision-making process among allies, which is in itself complex, but it is trained to work.” He rejected calls for a European army, saying that “it is not a road we should travel.” Norway is not a member of the EU.

NATO Secretary-General Mark Rutte said last week that Europe is incapable of defending itself without U.S. military support and would have to more than double current military spending targets to be able to do so.

“If anyone thinks here … that the European Union or Europe as a whole can defend itself without the U.S., keep on dreaming. You can’t,” Rutte told EU lawmakers in Brussels.

Europe and the United States “need each other,” he said.