President Donald Trump and the leaders of Denmark and Greenland signed a security agreement Tuesday that allows a major expansion of the U.S. military presence in Greenland while the island stays under Danish sovereignty.

The three leaders signed the deal on the sidelines of the United Nations General Assembly in New York. Trump sat alongside Danish Prime Minister Mette Frederiksen and Greenland Prime Minister Jens-Frederik Nielsen and said the pact would be good for Europe and the U.S. and "incredible" for Greenland, CNBC reported.

Under the agreement, the U.S. will modernize and expand Pituffik Space Base in northwest Greenland, which already runs missile warning, missile defense and space surveillance systems. Two new bases will open, at Narsarsuaq in the south and Mestersvig in the east, and Washington can add more defense areas later, according to Al Jazeera.

U.S. military aircraft may fly over and land anywhere in Greenland, including its territorial waters. The deal also grants undersea access and clears the way for Golden Dome, the administration's planned missile defense shield, the Deseret News reported.

Countries outside NATO cannot build military installations on the island or keep a persistent military presence there unless Washington, Copenhagen and Nuuk all agree. Investors from outside NATO and the European Union face limits in sensitive sectors.

There is no end date. If Greenland becomes independent, it stays in NATO and inherits Denmark's obligations under the pact.

The agreement updates a 1951 defense deal, CNBC reported. It ends a standoff that peaked in January, when Trump said the U.S. needed all of Greenland and would not rule out force. Frederiksen warned then that such a step could mean the end of NATO. About eight months of formal talks followed.

On Tuesday the tone was different. Frederiksen called the result "a deal that can last forever," Al Jazeera reported. Nielsen said it was a win for all three sides. Secretary of State Marco Rubio wrote on X that the deal costs U.S. taxpayers nothing.

NATO Secretary-General Mark Rutte and European Council President Antonio Costa welcomed the accord. Costa said it respects Greenland's sovereignty and its people's right to decide their own future.

The U.S. once operated 17 bases in Greenland. About 200 American troops are stationed there now, all at Pituffik.