Trump has insisted the United States needs the vast Arctic island for national and international security, and has refused to rule out the use of force to get it.

"We have to have it," he reiterated on Wednesday.

Vance and his wife Usha were to make a one-day visit to the US-run Pituffik Space Base in northwest Greenland, accompanied by National Security Advisor Mike Waltz, Energy Secretary Chris Wright, Utah Senator Mike Lee and former Homeland Security Advisor Julia Nesheiwat, who is Waltz's wife, according to journalists on board the flight from Washington.

They will meet US Space Force members and "check out what's going on with the security" of Greenland, Vance said in a video message this week.

Danish and Greenlandic officials, backed by the European Union, have insisted the United States will not get Greenland.

Danish Prime Minister Mette Frederiksen has denounced US plans to visit the Arctic island uninvited -- for what was initially a broader visit to Greenlandic society -- as "unacceptable pressure" on Greenland and Denmark.

A majority of Greenlanders oppose US annexation, according to a January poll.

The vice president angered Danes in early February when he said Denmark was "not doing its job (protecting Greenland), and it's not being a good ally".

A fuming Frederiksen quickly retorted that Denmark had long been a loyal US ally, fighting alongside the Americans "for many, many decades", including in Iraq and Afghanistan.

- Key base -

The Pituffik base is an essential part of Washington's missile defence infrastructure, its location in the Arctic putting it on the shortest route for missiles fired from Russia at the United States.

Known as Thule Air Base until 2023, it served as a warning post for possible attacks from the Soviet Union during the Cold War.

It is also a strategic location for air and submarine surveillance in the northern hemisphere, which Washington claims Denmark has neglected.

Vance is "right in that we didn't meet the American wishes for an increased presence, but we have taken steps towards meeting that wish", Marc Jacobsen, a senior lecturer at the Royal Danish Defence College, told AFP.

He said Washington needed to present more specific demands if it wanted a proper Danish response.

In January, Copenhagen said it would allocate almost $2 billion to beef up its presence in the Arctic and north Atlantic, acquiring specialised vessels and surveillance equipment.

Russian President Vladimir Putin said Thursday he considered Trump's plans for Greenland "serious", and expressed concern that "NATO countries, in general, are increasingly designating the far north as a springboard for possible conflicts".

- Frosty response -

Greenland is home to 57,000 people, most of them Inuits, and is believed to hold massive untapped mineral and oil reserves, though oil and uranium exploration are banned.

Energy Secretary Chris Wright, a former mining executive, told Fox News on Thursday he hoped the United States and Greenland could cooperate on mining to "bring jobs and economic opportunity to Greenland and critical minerals and resources to the United States".

Trump's desire to take over the ice-covered territory, which is seeking independence from Denmark, has been categorically rejected by Greenlanders, their politicians and Danish officials.

While all of Greenland's political parties are in favour of independence, none of them support the idea of joining the United States.

A new broad, four-party coalition government was announced in Greenland just hours before the US delegation's arrival, following elections earlier this month.

New prime minister Jens-Frederik Nielsen told reporters the territory needed unity at this time.

"It is very important that we put aside our disagreements and differences... because only in this way will we be able to cope with the heavy pressure we are exposed to from outside," he said.

The outgoing prime minister, Mute Egede, had on Monday reacted angrily to the uninvited US visit, as Greenland's parties were still negotiating to form a government.

"Our integrity and democracy must be respected without foreign interference," he said.

Initially, Vance's wife Usha was to travel alone to Greenland with her son and attend a dogsled race in the town of Sisimiut.

Locals said they had planned to give her a frosty reception, with several protests planned.

The visit to Sisimiut was then cancelled and replaced with the visit to the military base.