In a speech to the World Economic Forum in the Swiss ski resort, von der Leyen warned that Trump risked plunging US ties with the EU into a “downward spiral” over the autonomous Danish territory.

Trump, who will address the annual gathering of global elites on Wednesday, has put the transatlantic alliance to the test with his demand to take over Greenland.

Europe is weighing countermeasures after the US president threatened to impose tariffs on eight European countries over the Greenland standoff — although Washington has said any retaliatory levies would be “unwise”.

“The proposed additional tariffs are a mistake, especially between long-standing allies,” von der Leyen told the meeting of world business and political leaders.

“Plunging us into a downward spiral would only aid the very adversaries we are both so committed to keeping out of the strategic landscape. So our response will be unflinching, united and proportional,” she said.

Europe “must respond” to any trade war, Danish Prime Minister Mette Frederiksen later told her parliament, adding: “We are compelled to do so”.

Trump has pressed on with his Greenland campaign on his Truth Social platform, posting a fake photo of himself planting a flag in a landscape of rock and ice next to a sign reading “GREENLAND — US TERRITORY EST. 2026”.

He later wrote he had had a “very good” call with Nato secretary-general Mark Rutte over mineral-rich Greenland.

“I agreed to a meeting of the various parties in Davos, Switzerland,” he said late on Monday — after telling reporters he did not think European leaders would “push back too much” on his attempt to buy the vast island.

Trump argues he wants to protect Greenland from perceived Russian and Chinese threats, although analysts suggest Beijing is a small player in the region.

EU leaders will hold an emergency summit on Greenland in Brussels on Thursday.