French Foreign Minister Jean-Noel Barrot said that European allies, including Germany and Poland, are in discussions to formulate a response to Trump's threats.

"We want to take action, but we want to do so together with our European partners," Barrot told Reuters.

Barrot added that Trump's threats will be a subject of discussion at a meeting of foreign ministers from France, Germany and Poland later in the day.

The White House has formally stated that the military option to annex Greenland —an invasion followed by occupation— is on the table and the Trump administration remains committed to annexing the island.

"The President and his team are discussing a range of options to pursue this important foreign policy goal, and of course, utilising the US military is always an option at the Commander-in-Chief's disposal," the White House told CNN on Tuesday.

However, Barrot said that Secretary of State Marco Rubio told him the administration was instead looking to buy Greenland.

"I myself was on the phone yesterday with US Secretary of State Marco Rubio (…) who confirmed that this was not the approach taken … he ruled out the possibility of an invasion [of Greenland]," Barrot told Reuters.

US attack on Greenland would mean the death of Nato, says Denmark's PM

Since last week's invasion of Venezuela and the capture of Nicolas Maduro, the Trump administration has been emboldened in its expansionist agenda.

Trump and his supporters have repeatedly said they would annex Greenland and would invade the island if required. Even as Rubio has apparently sought to downplay these declarations, Danish Prime Minister Mette Frederiksen has said Trump's threats are serious.

Frederiksen added that a US invasion of Greenland would be the death of Nato — both Denmark and the United States are Nato members.

"If the United States chooses to attack another Nato country militarily, then everything stops. That is, including our Nato and thus the security that has been provided since the end of the Second World War," Frederiksen told Danish broadcaster TV2.

Trump has hinted that a US invasion of Greenland could begin soon. After invading Venezuela, he said, "Let's talk about Greenland in 20 days."

Trump said, "We'll worry about Greenland in about two months. Let's talk about Greenland in 20 days."