US President Donald Trump has further flared the already tense transatlantic relationship, suggesting in an interview on Thursday that NATO allies would not come to Washington's support if asked — despite all of them responding the only time NATO's mutual defense clause was invoked. 

Speaking to Fox News from Davos, Trump said, "I'm not sure" if NATO allies would be there "if we ever needed them and that's really the ultimate test."

"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,” he added.

Article 5 of NATO's founding treaty stipulates that if one member of the alliance is attacked, all other members should come to its defense. NATO's mission to Afghanistan was the only time this Article was activated — a step that was taken by the United States.

Britain said the US president was "wrong to diminish" the role of NATO troops in Afghanistan.

The US Department of Defense says the US lost some 2,460 troops in Afghanistan. In addition, 457 British troops, over 150 Canadian troops, 90 French service personnel, 62 German soldiers and 44 Danish troops were also killed. The latter is among NATO's highest per-capita deaths.

How the UK responded to Trump's 'insulting' claims

British Prime Minister Keir Starmer called the president's comments "insulting and frankly appalling."

"I ‍consider President Trump's ​remarks ​to be insulting and frankly appalling, and I'm not surprised they've caused ‍such hurt for the loved ​ones of those who were killed ⁠or ​injured," Starmer said on Friday.

His official spokesman reminded Trump of the hundreds of troops killed in Afghanistan.

"Their sacrifice and that of other NATO forces was made in the service of collective security and in response to an attack on our ally," the spokesman said. "We are incredibly proud of our armed forces and their service and sacrifice will never be forgotten."

Britain's former-Prime Minister Tony Blair was among the staunchest supporters of former US President George W. Bush's so-called "war on terror" despite wide criticism.

After the September 11, 2001, terror attacks and when Washington invoked Article 5 of the NATO treaty, Blair said the UK would "stand shoulder to shoulder" with the US.     

Over 150,000 British troops served in Afghanistan, the second largest contingent after the US.

British Defense Secretary John Healey said the UK and NATO allies "answered the US call" at the time, and honored the British personnel who lost their lives in Afghanistan.

"Those British troops should be remembered for who they were: heroes who gave their lives in service of our nation," he said.

Ben Obese-Jecty, a lawmaker who served in Afghanistan as a captain in the Royal Yorkshire Regiment, said it was "sad to see our nation's sacrifice, and that of our NATO partners, held so cheaply by the president of the United States."

Britain's veterans minister, Alistair Carns, whose own military service included five tours, including alongside American troops in Afghanistan, called Trump's claims "utterly ridiculous."

"We shed blood, sweat and tears together. ‍Not everybody came home," he said in a video posted on X. He later shared a video purportedly showing fighting in Afghanistan with the caption "on the frontline."

Lucy Aldridge, whose son William died aged 18 in Afghanistan, told British newspaper The Mirror that Trump's remarks were "extremely upsetting."

Trump avoided Vietnam War draft with bone spurs

Some politicians noted that the US president had avoided the draft for the Vietnam War, citing bone spurs in his feet. Unable to remember which foot had bone spurs when questioned, Trump has been accused of dodging the draft.

"Trump avoided military service 5 times," Ed Davey, leader of Britain's centrist Liberal Democrats, wrote on X. "How dare he question their sacrifice."

Trump's latest comments come amid heightened tensions between the US and NATO's European member-states, after the US president intensified his push to acquire the semiautonomous Arctic island of Greenland, currently part of the Kingdom of Denmark.

Several European officials, including the Danish leader, warned that such a move would be considered the end of NATO.

Earlier this week, following a meeting with NATO Secretary-General Mark Rutte in Davos, Trump announced a "framework" agreement over Greenland, and walked back on threats to hit eight European countries with tariffs.

Edited by: Sean Sinico