U.K. Prime Minister Keir Starmer on Friday denounced U.S. President Donald Trump's claim that troops from NATO allies avoided the front line in Afghanistan as "insulting," as anger grows at the president's remarks.

In an interview with Fox News aired on Thursday, Trump appeared unaware that 457 British soldiers were among NATO troops who died during the conflict in Afghanistan following the Sept. 11, 2001, attacks on the United States.

"They'll say they sent some troops to Afghanistan," Trump told the U.S. outlet, referring to NATO allies.