Speaking at the signing ceremony, Trump said: “We going to have a tremendous relationship, a secure relationship.”
“This is tremendous for Europe and for the United States, for everybody, and for Greenland it’s going to be incredible.”
Meanwhile, Frederiksen described the signing of the deal as a “milestone in our long-standing co-operation”.
“Seventy-five years ago we entered into an agreement about the defence of Greenland. Today, we’re signing an even bigger and better agreement – a deal that can last forever.”
The Danish prime minister stressed that the agreement “respects sovereignty and territorial integrity of the Kingdom of Denmark, as well as Greenland’s right to self-determination”.
Jens-Frederik Nielsen said that “for Greenland, it is not only an agreement about us, it is [an] agreement with us.
“It takes into account the people of Greenland, our rights, our livelihoods and the development of our country.
“Greenland matters for North American security and for transatlantic security,” he said, adding that the Nato had a key role to play in the North Atlantic in a changing security situation.
The agreement also confirmed Greenland would remain in Nato if it were to gain independence from Denmark.
The 1951 agreement already allowed the US to send as many troops as it wanted to Greenland. Washington already has more than 100 military personnel permanently stationed at its Pituffik base.
Trump had tried for months to purchase or annex Greenland, arguing that it was vulnerable to adversaries, including Russia and China.
He argued the Arctic island was an essential piece of his plan to build a futuristic “Golden Dome” defence system to protect the US against missile attacks.
However the deal only mentions the project once, and contains no concrete proposal.
The island has vast – and largely untapped – reserves of rare earth minerals, many of which are crucial for technologies including mobile phones and electric vehicles.
Trump said last week that the new deal came with “no cost to the United States”.
A Nato spokesperson said shortly afterwards that the military alliance welcomed the deal, which would “help advance security, stability and cooperation in this vital region”.
