Denmark’s prime minister insisted on Monday that Greenland is not for sale and called for a robust response from her European Union partners should U.S. President Donald Trump press ahead with his threat to take control of the island.

“I will never support the idea of fighting allies. But of course, if the U.S. puts tough terms on Europe, we need a collective and robust response,” Danish Prime Minister.

Greenland, home to a large U.S. military base, is an autonomous territory of Denmark, a longtime U.S. ally. Last month, Trump left open the possibility that the American military might be used to secure Greenland, as well as the Panama Canal. “We need Greenland for national security purposes,” he said.

Frederiksen said she has “great support” from her EU partners on the fact “that everybody has to respect the sovereignty of all national states in the world, and that Greenland is today a part of the Kingdom of Denmark. It’s part of our territory and it’s not for sale.”