MIAMI (AP) — President Donald Trump told the widow of a soldier killed in an ambush in Niger that her husband "knew what he signed up for," according to a Florida congresswoman who says she heard part of the conversation on speakerphone.

Rep. Frederica Wilson said she was in the car with Myeshia Johnson on Tuesday on the way to Miami International Airport to meet the body of Johnson's husband, Sgt. La David Johnson, when Trump called.

When asked by Miami station WPLG if she indeed heard Trump say that she answered: "Yeah, he said that. To me, that is something that you can say in a conversation, but you shouldn't say that to a grieving widow." She added: "That's so insensitive."

But in a Wednesday morning tweet, Trump said Wilson's description of the call was "fabricated."

"Democrat Congresswoman totally fabricated what I said to the wife of a soldier who died in action (and I have proof). Sad!" Trump wrote without specifying what proof he had.

Sgt. Johnson was among four servicemen killed in the African nation of Niger earlier this month. They died when militants thought to be affiliated with the Islamic State group ambushed them while they were patrolling in unarmored trucks with Nigerien troops.

Wilson, a Democrat, said she did not hear the entire conversation and Myeshia Johnson told her she couldn't remember everything that was said when asked it about it later.

The White House didn't immediately comment.

Trump has been criticized for not reaching out right away to relatives of the four killed in Niger. On Monday, Trump said he'd written letters that had not yet been mailed. His aides said they had been awaiting information before proceeding.