Denmark is ready to defend every inch of NATO, including Danish territory, Prime Minister Mette Frederiksen said in Ankara on Wednesday, a day after U.S. President Donald Trump reiterated that Greenland should be controlled by the United States.

Frederiksen made the remarks amid renewed tensions between Washington and Copenhagen over Trump’s comments about Greenland, a semi-autonomous Danish territory. She also said Greenland is not for sale and reiterated Denmark’s view that allies should stand up for one another if something happens to any member.

Greenland’s Prime Minister Jens-Frederik Nielsen also rejected Trump’s remarks, saying repeated calls for the takeover or control of Greenland do not change Greenland’s position. Nielsen reiterated that Greenland is not for sale.

Denmark’s Foreign Minister Lars Lokke Rasmussen said Denmark continues diplomatic efforts involving Greenland and the U.S. He said Denmark and the U.S. have an agreement to explore a solution within the kingdom’s “red lines” that also addresses what he described as the U.S.’ legitimate security interests.

Rasmussen said Denmark believes it is possible to reach a deal that satisfies Greenland, Denmark and the U.S., including by expanding a 1951 U.S.-Danish defense agreement that provides broad U.S. military access to Greenland.

The Greenland issue has strained relations between NATO allies as the U.S. and European countries also contend with broader alliance questions, including defense commitments and the future direction of security cooperation.