By Agence France-Presse
Trump moved quickly to dispute descriptions of his conversation with the pregnant widow of Sergeant La David Johnson, 25, who was one of four US service members killed in a jihadist ambush October 4.
But two accounts of his condolence call suggest the president struggled to convey an empathetic tone.
"President Trump did disrespect my son and my daughter and also me and my husband," Sergeant La David Johnson's mother, Cowanda Jones-Johnson, told the Washington Post.
She said she agreed with an earlier account of the call, given by a lawmaker who said she heard part of the conversation and accused Trump of insensitivity for telling Johnson's pregnant widow Myeshia Johnson that the young soldier "knew what he was signing up for."
"I didn't hear the whole phone call, but I did hear him say, 'I'm sure he knew what he was signing up for, but it still hurts,'" Frederica Wilson, a Democratic congresswoman from Florida, told CNN.
Trump denied making the comments, tweeting Wednesday: "Democrat Congresswoman totally fabricated what I said to the wife of a soldier who died in action (and I have proof). Sad!"
He later told reporters: "I did not say what she said," and that "I had a very nice conversation."
When asked about what proof he could offer, Trump said: "Let her make her statement again then you will find out."
Johnson was among four US soldiers killed October 4 in Niger, where Islamic State fighters have established a presence.
The military has released few details about what happened, and on Tuesday Senator John McCain, who heads the Senate Armed Services Committee, said the Trump administration was not being forthcoming with information.
The Miami native's body was returned home Tuesday afternoon. His wife Myeshia, who is expecting the couple's third child, sobbed loudly while cradling his coffin after it was taken off a military plane.
After Trump's call, Myeshia "was crying, she broke down. And she said 'he didn't even know his name,'" Wilson said, referring to Trump and the dead soldier.
- Finding the right tone -
Trump had faced criticism for not contacting the families of the soldiers killed in Niger right away.
On Monday, he said he had written them letters and would call soon, while accusing his predecessor Barack Obama of neglecting to call as many grieving families as himself.
He also suggested on a call to Fox News radio Tuesday that Obama had not made a condolence call to retired Marine general John Kelly, Trump's White House chief of staff, after his son was killed in action in Afghanistan.
The statements sparked outrage from former Obama aides, who said Trump's claims were baseless.
Trump has repeatedly struggled to strike the right tone during times of national disaster, moments when America looks to its leader for comforting remarks.
He recently told hurricane-ravaged Puerto Rico that his willingness to help the US territory was not unlimited, and after a Las Vegas mass shooting that left 58 dead and more than 500 wounded, Trump offered his "warmest condolences."
Separately, the Post reported Wednesday that Trump had promised $25,000 to the father of a soldier killed in Afghanistan in June, and to help him establish an online fundraiser -- neither of which happened.
The check was also sent Wednesday, the same day as the Post report, according to CNN, which quoted a White House official.
The White House sent out a terse statement on the matter.
"The check has been sent. It's disgusting that the media is taking something that should be recognized as a generous and sincere gesture, made privately by the president, and using it to advance the media's biased agenda," spokeswoman Lindsay Walters said.
It took this long to get the check out because several government agencies may be involved when the president interacts with the public, especially in cases involving his personal funds, CNN quoted a White House official as saying.