EU leaders scramble to avoid friction with the US under Trump and avoid a 'stupid tariff war'

Since taking office last month, U.S. President Donald Trump has threatened to impose tariffs on EU imports and refused to rule out military force to take control of Greenland, an autonomous territory of NATO ally Denmark.

Trump has also mystified Europeans by showing little sign of how he intends to end the war in Ukraine within six months as promised, let alone in a day, as he boasted while campaigning last year.

"We have to do everything to avoid this totally unnecessary and stupid tariff war or trade war," the Polish prime minister told reporters in Brussels, where EU leaders met for talks on boosting and improving military spending and ramping up Europe's defense industry.

Tusk said Trump's threats amount to "a serious test" of European unity, and "in a very strange context, because it's the first time where we have such a problem among allies."

French President Emmanuel Macron said the EU is "a power that stands its ground" and that if hit with tariffs, the 27-nation bloc "would have to make itself respected." He said Trump's threats are "pushing Europeans to be more united, more active in addressing their collective security challenges."

Trump slapped tariffs on European steel and aluminum during his first term, and EU leaders have already been in contact with Canadian Prime Minister Justin Trudeau since Canada imposed retaliatory duties on U.S. goods in response to a 25% tariff levied by Trump. The U.S. president later on Monday agreed to a 30-day pause on his tariff threat as America's two largest trading partners took steps to appease his concerns about border security and drug trafficking.

European Commission President Ursula von der Leyen underlined that ties between the bloc and the United States are part of "our most consequential relationship. It is fundamental to promoting peace, security and prosperity."

But she warned that "there are clearly new challenges and growing uncertainty" and the EU stands ready to defend itself. "When targeted unfairly or arbitrarily, the European Union will respond firmly," von der Leyen told reporters after the meeting.

Meanwhile, Denmark's prime minister again insisted on Monday that Greenland isn't for sale and called for a robust response from the EU should U.S. Trump press ahead with his threat to take control of the island.

"I will never support the idea of fighting allies. But of course, if the U.S. puts tough terms on Europe, we need a collective and robust response," Danish Prime Minister Mette Frederiksen told reporters.

Last month, Trump left open the possibility that the American military might be used to secure Greenland, as well as the Panama Canal. "We need Greenland for national security purposes," he said.

Frederiksen said she has "great support" from her EU partners on the fact "that everybody has to respect the sovereignty of all national states in the world, and that Greenland is today a part of the Kingdom of Denmark. It's part of our territory and it's not for sale."

European Council President Antonio Costa, noting that the EU has stood beside Ukraine in defense of its borders, said of Greenland: "Of course, we will stand also for these principles, all the more so if the territorial integrity of a member state of the European Union is questioned."

Frederiksen acknowledged U.S. concerns about security in the Arctic Region, where Russia and China have been increasingly active.

"I totally agree with the Americans that the High North, that the Arctic region is becoming more and more important when we are talking about defense and security and deterrence," Frederiksen said, adding that the U.S. and Denmark could have "stronger footprints" in Greenland, in security terms.

"They are already there and they can have more possibilities," she said, underlining that Denmark itself can also "scale up" its security presence. "If this is about securing our part of the world, we can find a way forward," Frederiksen said.

Last week, her government announced a roughly 14.6 billion kroner (nearly $2 billion) agreement with parties including the governments of Greenland and the Faeroe Islands to "improve capabilities for surveillance and maintaining sovereignty in the region."

It would include three new Arctic naval vessels, two additional long-range surveillance drones and satellite capacity, the Danish Defense Ministry said.