Danish Prime Minister Mette Frederiksen warned President Donald Trump to stop threatening to acquire Greenland just a day after the U.S. carried out a military operation that captured Venezuelan leader Nicolas Maduro.

“The Kingdom of Denmark — and thus Greenland — is part of NATO and is therefore covered by the alliance’s security guarantee. We already have a defense agreement between the Kingdom and the United States today, which gives the United States wide access to Greenland,” Frederiksen said Sunday, in a statement.

“I would therefore strongly urge the United States to stop the threats against a historically close ally and against another country and another people who have said very clearly that they are not for sale,” she said.

The warning from Frederiksen comes after Trump was quoted by The Atlantic magazine, saying, “We do need Greenland, absolutely.”

Trump ordered a military operation over the weekend that captured Venezuelan President Nicolas Maduro and his wife. The pair has been brought to the U.S. on drug-related charges.