Donald Trump told the widow of a fallen US soldier that “he knew what he was signing up for”, it was claimed yesterday as an attempted condolence backfired spectacularly.

The US President was said to have made the comment when calling the wife of La David Johnson, a 25-year-old killed recently in Niger, West Africa.

Two people listening into the call - including Mr Johnson’s mother - confirmed he made the remark and called it “disrespectful”.

However Mr Trump denied the claim in the strongest terms and said he had “proof” the words had not been spoken, implying a recording existed.

The row comes after Mr Trump faced criticism earlier this week for how he consoles relatives of America’s war dead, when he in turn criticised Barack Obama.

The trigger had been the killing of four US Special Forces soldiers in Niger, which Mr Trump did not publicly acknowledge for 12 days.