President Donald Trump signed an agreement with Denmark and Greenland on Tuesday.

The deal aims to strengthen Arctic and North Atlantic security.

It also eases tensions over Trump's repeated calls for Greenland to become part of the United States.

The signing took place on the sidelines of the U.N. General Assembly in New York.

Trump said the deal was tremendous for Europe, the United States and everyone, and incredible for Greenland.

For months, Trump had said he wanted Greenland to join the U.S.

He also threatened to seize the semiautonomous territory from Denmark, a NATO ally.

On Tuesday, he did not answer questions about whether a U.S. acquisition was off the table.

Officials from the three sides negotiated for months behind the scenes.

Danish Prime Minister Mette Frederiksen had warned that a U.S. takeover would mean the end of the Atlantic alliance.

The agreement lets Washington modernize and expand its activities at the Pituffik Space Base in northwest Greenland.

The U.S. can also set up defense areas at Narsarsuaq in the south and Mestersvig in the east.

It may establish more defense areas and strengthen its military operations or facilities.

Trump told the U.N. General Assembly that the U.S. would build two very major military bases.

No non-NATO country may set up military installations in Greenland or keep a persistent military presence there unless the signatories agree.

The accord has no end date.

If Greenland becomes independent, it will agree to stay in NATO and take on Denmark's rights and obligations under the deal.

Researcher Mikkel Runge Olesen said Greenland and Denmark can end the crisis without compromising on sovereignty.

He said the U.S. gets a somewhat more favorable deal than under the existing defense treaty.

But he warned that lost trust will take decades to rebuild.

Frederiksen called it a deal that can last forever.

Greenland's prime minister, Jens-Frederik Nielsen, called it a win-win-win agreement.