United States President Donald Trump on Friday threatened to impose tariffs on countries which do not back the US taking control of Greenland.

The US President did not elaborate on the details but has in the past stated that the United States needs Greenland from the point of view of “national security”.

“I may put a tariff on countries if they don’t go along with Greenland, because we need Greenland for national security,” Bloomberg quoted Trump as saying at a White House event on healthcare.

Trump has insisted, for months now, that the US should control Greenland, a self-governing territory which is part of the kingdom of Denmark.

However, while the White House has confirmed that “all options are on the table” regarding the US taking over the territory, this is the first time that Trump has threatened tariffs over nations not backing the proposal.

This comes a day after European countries sent small numbers of military troops to Greenland, even as Denmark said it was pressing on with plans to establish “larger and more permanent” NATO presence for the security of the island, according to Reuters news agency.

The display of support towards the territory was also meant to help Denmark prepare military exercises, and followed a meeting of officials from the US, Denmark and Greenland.

On Friday, a group of US senators and representatives met lawmakers in the Danish parliament, with protests against Trump’s plans due across Denmark due to Saturday, according to Bloomberg.

Danish Foreign Minister Lars Lokke Rasmussen has been attending meetings in Washington with members of the US Congress for a week now, on the heels of talks with US Vice President J D Vance and Secretary of State Marco Rubio.

After the talks with Vance and Rubio, Rasmussen said a “fundamental disagreement” with Trump over Greenland remained. Both sides had, during the meetings, agreed to form a working group to discuss ways to work through differences, according to AP.