Joe Biden made a blunder during a speech when he asked if a deceased congresswoman was in the audience.
The US president made the gaffe at a conference on hunger, nutrition and health after apparently forgetting that Jackie Walorski, the former Republican representative for the state of Indiana, died in a car crash in August.
Mr Biden, 79, looked around the room in Washington and said: "Jackie, are you here? Where's Jackie? She must not be here" on Wednesday.
The blunder saw White House press secretary Karine Jean-Pierre field a flurry of questions during the press briefing that followed.
She repeated more than a dozen times that Ms Walorski was "top of mind" for Mr Biden - who is due to meet with the congresswoman's family on Friday to sign a bill renaming a veterans' affairs clinic in Indiana after her.
Ms Jean-Pierre did not acknowledge the president had misspoken and did not apologise for the error.
"My answer is certainly not going to change," she told journalists.
"All of you may have views on how I am answering it, but I'm answering the question to the way that he saw it and to the way that we see it."
Ms Walorski's brother, Keith, told the New York Post that he was not angry with the president, who called Ms Walorski's family to offer his condolences after she died.
Mr Biden is "doing the best he can do with what he's got right now", he said.
Mr Walorski added: "Yeah it was a big mess-up today. Inexcusable? No. Unforgivable? No. I'm not gonna hold it against him. I just feel sorry for him."