US President-elect Donald Trump has said he would not rule out the use of military force to seize control of the Panama Canal and Greenland, as he claimed both to be vital to US national security.

Speaking to reporters on Tuesday night, less than two weeks before he takes office on January 20, Mr Trump left open the use of the US military to secure both territories.

“I’m not going to commit to that,” Mr Trump said when asked if he would rule out the use of the military.

“It might be that you’ll have to do something. The Panama Canal is vital to our country,” he said, adding: “We need Greenland for national security purposes.”

Greenland, home to a large US military base, is an autonomous territory of Denmark, a long-time US ally and a founding member of Nato.

The Panama Canal has been solely controlled by Panama for more than 25 years. The US returned the Panama Canal Zone to the country in 1979 and ended its joint partnership in controlling the strategic waterway in 1999.

Addressing Trump’s comments in an interview with Danish broadcaster TV2, Prime Minister Mette Frederiksen called the US Denmark’s “most important and closest ally,” and said she did not believe that it will use military or economic power to secure control over Greenland.

Ms Frederiksen repeated that she welcomed the US taking a greater interest in the Arctic region, but that it would “have to be done in a way that is respectful of the Greenlandic people,” she said.

“At the same time, it must be done in a way that allows Denmark and the United States to still co-operate in, among other things, Nato,” Ms Frederiksen said.

Earlier, Mr Trump posted a video of his private plane landing in Nuuk, the Arctic territory’s capital, in a landscape of snow-capped peaks and fjords.

“Don Jr and my Reps landing in Greenland,” Mr Trump wrote.

“The reception has been great. They, and the free world, need safety, security, strength, and peace! This is a deal that must happen. MAGA. Make Greenland Great Again!”

In a statement, Greenland’s government said Donald Trump Jnr’s visit was taking place “as a private individual” and not as an official visit, and Greenlandic representatives would not meet him.

Panamanian Foreign Minister Javier Martinez-Acha said his government hasn’t had formal contact with Mr Trump or representatives of the incoming administration, but reiterated previous comments from the country’s president, Jose Raul Mulino, who said last month that the canal will remain in Panamanian hands.

“The sovereignty of our canal is not negotiable and is part of our history of struggle and an irreversible conquest,” Mr Martinez-Acha said.

Mr Trump has also floated having Canada join the United States as the 51st state. He said on Tuesday that he would not use military force to invade the country.