WASHINGTON, Jan. 26 (Xinhua) -- Emotions are running high in Europe following U.S. President Donald Trump's military threats and his downplaying of contributions made by allied troops in Afghanistan.

Trump has triggered outrage among allies in the North Atlantic Treaty Organization (NATO) after questioning whether they would come to Washington's aid in times of need.

"We've never needed them. We have never really asked anything of them. You know, they'll say they sent some troops to Afghanistan, or this or that. And they did -- they stayed a little back, a little off the front lines," Trump said Thursday in an interview with Fox News in Davos, Switzerland, sparking a firestorm of criticism.

The comments incensed European leaders, with British Prime Minister Keir Starmer denouncing Trump's statement as "insulting and frankly appalling" since British forces suffered casualties in the U.S. war in Afghanistan.

Polish Prime Minister Donald Tusk also lambasted Trump's comments in a social media post, pointing out that his country, too, lost troops in Afghanistan.

This latest controversy comes on the heels of a tense dispute with European leaders over Greenland, after Trump said military action would be a possible option in his bid to acquire the largely Arctic island, a self-governing territory within the Kingdom of Denmark.

Danish Prime Minister Mette Frederiksen said that while security, investment and economic issues could be negotiated, "we cannot negotiate on our sovereignty."

While Trump later claimed to have secured the framework of a deal with NATO regarding Greenland's future, his threats and aggressive rhetoric prompted European leaders to denounce any military aggression on Greenland as "neo-colonialism."

The United States wanted to "weaken and subordinate Europe" by demanding "maximum concessions" and implementing tariffs that were "fundamentally unacceptable -- even more so when they are used as leverage against territorial sovereignty," French President Emmanuel Macron said at the recent World Economic Forum (WEF) in Davos, Switzerland.

EU foreign policy chief Kaja Kallas said Thursday that "transatlantic relations have definitely taken a big blow over the last week."

Former European Council President Charles Michel told CNN that the transatlantic relationship "as we've known it for decades is dead."

Critics also argued that Trump's suggestion of using military force in the Greenland dispute would violate international treaties, including the UN Charter, which forbids the threat or use of force against the territorial integrity or political independence of any state.

Moreover, as both the United States and Denmark are members of NATO, an attack on Greenland would also violate the North Atlantic Treaty.

Trump has since backed down from his threats of military action and tariffs, following strong condemnation from EU leaders.

For its part, the Trump administration has emphasized that Greenland is critical to U.S. national security.

Speaking live on stage at the WEF, U.S. Treasury Secretary Scott Bessent said that Trump "believes that Greenland is essential for the Golden Dome missile shield."

"Greenland is becoming more and more attractive for foreign conquest," Bessent said. "And (Trump) very strongly believes that it must be part of the United States to prevent a conflict, rather than getting the U.S. engaged and exposed into a hot conflict."

When asked if Greenland is crucial to U.S. national security, Michael O'Hanlon, a senior fellow at the Brookings Institution, told Xinhua: "It is important, but we are already able to protect it. In fact, by treaty, we are already obliged to."

Greenland hosts a key U.S. military base, and with Arctic ice melting, new shipping routes and access to natural resources are becoming increasingly viable. This has driven much of the U.S. interest in the island, according to media reports.