President Donald Trump on Saturday appeared to offer an olive branch to Britain in a row over the role of UK soldiers in Afghanistan, calling them "among the greatest of all warriors."

In an interview with Fox News aired on Thursday, Trump claimed NATO had sent "some troops" but "stayed a little back, a little off the front lines."

Trump also repeated his suggestion that the alliance would not come to the aid of the US if asked to do so.

Other European countries have reacted sharply to his comments, discounting what NATO troops did in Afghanistan, with French President Emmanuel Macron the latest to comment Saturday.

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"I fully understand that Danish veterans have said no words can describe how much this hurts," Danish Prime Minister Mette said Saturday on Facebook.

"It is unacceptable that the American president questions the commitment of allied soldiers in Afghanistan," she added.

In the interview, Trump appeared unaware that 457 British soldiers were among NATO troops who died during the conflict in Afghanistan following the September 11, 2001, attacks on the US.

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

The White House rejected Starmer's comments and defended Trump.

"President Trump is absolutely right – the United States of America has done more for NATO than any other country in the alliance has done combined," Taylor Rogers, a White House spokeswoman, said in a statement sent to AFP.

Following the 9/11 attacks, Britain and a number of other allies joined the US from 2001 in Afghanistan after it invoked NATO's collective security clause.

As well as Britain, troops from other NATO ally countries – including Canada, France, Germany, Italy, and Denmark – also died.