The mother of a US Army sergeant killed in Niger has said Donald Trump showed “disrespect” to the soldier’s loved ones as they drove to the airport to collect his body.

The president, engulfed in controversy over the appropriate way for presidents to show compassion for killed soldiers, strongly disputed that account.

Sergeant La David Johnson was one of four US military personnel killed nearly two weeks ago whose families had not heard from Mr Trump until Tuesday.

Congresswoman Frederica Wilson said Mr Trump told the widow Sgt Johnson “knew what he signed up for”.

The Florida Democrat said she was in the car with the widow, Myeshia Johnson, on the way to Miami International Airport to meet the body when Mr Trump called to offer condolences.

Sgt Johnson’s mother, Cowanda Jones-Johnson, told the Associated Press that the congresswoman’s account was correct.

“Yes the statement is true,” Ms Jones-Johnson said. “I was in the car and I heard the full conversation.”

Mr Trump later tweeted: “Democrat Congresswoman totally fabricated what I said to the wife of a soldier who died in action (and I have proof). Sad!”

And in a White House meeting on tax reform, he added that he “didn’t say what that congresswoman said, didn’t say it at all. She knows it”.

Ms Wilson did not back down from her account, suggesting Mr Trump “never wants to take ownership” of a mistake.

“If you are the leader of the free world, if you are president of the United States and you want to convey sympathy to a grieving family, a grieving widow, you choose your words carefully,” she said. “And everyone knows that Donald Trump does not choose his words carefully.”

“She was crying for the whole time,” Ms Wilson said of the widow. “And the worst part of it: when he hung up, you know what she turned to me and said? She said he didn’t even remember his name.”

Like presidents before him, Mr Trump has made personal contact with some families of the fallen but not all.

What is different is that Mr Trump alone has picked a political fight over who has done better to honour the war dead and their families.

He placed himself at the top of the list, saying: “I think I’ve called every family of someone who’s died,” while past presidents did not.

His delay in publicly discussing the men lost in Niger did not appear to be extraordinary, judging from past examples, but his politicisation of the matter is.

Democrats and some former government officials were livid, accusing Mr Trump of “inane cruelty” and a “sick game”.

Democratic senator Tammy Duckworth, an Iraq veteran who lost both legs when her helicopter was attacked, said: “I just wish that this commander in chief would stop using Gold Star families as pawns in whatever sick game he’s trying to play here.”

Some Gold Star families who lost members in wartime told AP of acts of kindness from Mr Obama and George W Bush when those commanders in chief consoled them.

Mr Trump initially claimed that only he among presidents made sure to call families. Mr Obama may have done so on occasion, he said, but “other presidents did not call”.

He equivocated on Tuesday as the record made plain that his characterisation was false. “I don’t know,” he said of past calls. But he said his own practice was to call all families of the war dead.