US President Donald Trump on Saturday vowed to implement a wave of increasing tariffs on European allies until the United States is allowed to buy Greenland, escalating a row over the future of Denmark's vast Arctic island.

In a post on Truth Social, Trump said additional 10 percent import tariffs would take effect on February 1 on goods from Denmark, Norway, Sweden, France, Germany, the Netherlands, Finland and Great Britain — all already subject to tariffs imposed by Trump.

Those tariffs would increase to 25 percent on June 1 and would continue until a deal was reached for the US to purchase Greenland, Trump wrote.

Trump has repeatedly insisted he will settle for nothing less than ownership of Greenland, an autonomous territory of Denmark. Leaders of both Denmark and Greenland have insisted the island is not for sale and does not want to be part of the United States.

A Reuters/Ipsos poll of US residents this week found that less than one in five respondents support the idea of acquiring Greenland.

The president has repeatedly said Greenland is vital to US security because of its strategic location and large mineral deposits, and has not ruled out using force to take it. European nations this week sent military personnel to the island at Denmark's request.

"These Countries, who are playing this very dangerous game, have put a level of risk ⁠in play that is not tenable or sustainable," Trump wrote.

Protesters in Denmark and Greenland demonstrated on Saturday against Trump's demands and called for the territory to be left to determine its own future.

The countries named by Trump on Saturday have backed Denmark, warning that the US military seizure of a territory in Nato could collapse the military alliance that Washington leads.

"The president's announcement comes as a surprise," Denmark's Foreign Minister Lars Lokke Rasmussen said in a statement.

British Prime Minister Keir Starmer was unusually blunt in condemning Trump’s threat, saying on X that his country would raise the issue directly with Washington.

"Applying tariffs on allies for pursuing the collective security of Nato allies is completely wrong," Starmer said.

European Commission President Ursula von der Leyen and European Council President Antonio Costa said in separate but identical posts on X that the European Union stood in "full solidarity" with Denmark and Greenland.

"Tariffs would undermine transatlantic relations and risk a dangerous downward spiral. Europe will remain united, coordinated, and committed to upholding its sovereignty," they said.

Officials from Norway, Sweden, France and Germany reiterated support for Denmark on Saturday and said tariffs should not be part of Greenland discussions.

Cyprus, which currently holds the EU presidency, said it has called for an emergency meeting of ambassadors from the union's 27 countries on Sunday.

Saturday's threat could derail tentative deals Trump struck last year with the European Union and Great Britain. The deals included baseline levies of 15 percent on imports from Europe and 10 percent on most British goods.

"The biggest danger, it seems to me, is his decision to treat some EU countries different from others," said William Reinsch, a trade expert at the Centre for Strategic and International Studies.

"I'm not surprised … It may well convince the European Parliament that it is pointless to approve the trade agreement with the US, since Trump is already bypassing it."

Some US senators also pushed back. "Continuing down this path is bad for America, bad for American businesses and bad for America's allies," Senators Jeanne Shaheen and Thom Tillis, bipartisan co-chairs of the Senate Nato Observer Group, said in a statement. (Reuters)