The White House on Tuesday declined to "guarantee" that Donald Trump had never been recorded using the n-word as he faced claims of racism from a former aide.
Asked if she could say with absolute certainty the American people would never hear such a tape, Sarah Sanders, the White House press secretary, said: "I cannot guarantee anything".
The surprise admission came after former White House aide Omarosa Manigault Newman claimed Mr Trump had been recorded using the racial slur while filming his reality TV show The Apprentice.
Ms Sanders said: "I can’t guarantee anything. But I can tell you that the president addressed this question directly on Twitter. I can tell you that I’ve never heard it."
When pressed on the issue a second time, Ms Sanders said: "Look, I haven’t been in every single room. I can tell you the president has addressed this directly. He has addressed it directly to the American people.
"I can tell you what the focus and heart of the president is, and that is helping all Americans".
Mr Trump has vehemently denied using the slur.
Ms Manigault Newman, a former Apprentice star, has claimed to have spoken to three sources who confirmed the existence of a tape in which Mr Trump uses the n-word.
The former aide, once one of the president’s most prominent black supporters, has made the claims in a tell-all memoir detailing her year in the White House.
She has also released a string of covert recordings she made of officials as she promoted the release of her book, Unhinged, on Tuesday.
The US president has vehemently denied using the n-word and lashed out at his former aide, referring to her as a "dog" as he denounced her claims.
Mr Trump also claimed that the show’s British former producer, Mark Burnett, had called him to confirm that no such tape existed.
"When you give a crazed, crying lowlife a break, and give her a job at the White House, I guess it just didn’t work out. Good work by General Kelly for quickly firing that dog!" he tweeted.
When you give a crazed, crying lowlife a break, and give her a job at the White House, I guess it just didn’t work out. Good work by General Kelly for quickly firing that dog!
— Donald J. Trump (@realDonaldTrump) August 14, 2018
Critics have condemned Mr Trump for what they said were racial and sexist undertones to his tweet.
On Tuesday, CBS News released another of Ms Manigault Newman’s records from October 2016 in which she and several other Trump campaign aides discuss the alleged tape of Mr Trump using a racial epithet during The Apprentice.
The recording appears to show Ms Manigault Newman discussing with Trump campaign aides Katrina Pierson and Lynne Patton how to respond to the remarks.
"I’m trying to find out at least what context it was used in, to help us maybe try to figure out a way to spin it," a woman, identified as Ms Pierson, can be heard saying.
Ms Manigault Newman has hinted that she has several more tapes of conversations with White House staff and is willing to hand them over to the Special Counsel’s Office investigating alleged Russian collusion in the 2016 presidential election.
Mr Trump’s re-election campaign announced on Tuesday that it is taking legal action against Ms Manigault Newman over her public bashing of the president.
The campaign has filed for arbitration against the former White House aide arguing that she has violated a confidentiality agreement she signed in 2016, while she was still a member of Mr Trump’s presidential campaign.
The claim, filed with the American Arbitration Association in New York, highlights statements Ms Manigault Newman made during her time on Mr Trump’s campaign as well as in the White House, as well as her recent release of several tape recordings of White House officials.
“President Trump is well known for giving people opportunities to advance in their careers and lives over the decades, but wrong is wrong, and a direct violation of an agreement must be addressed and the violator must be held accountable,” a campaign official told The Washington Examiner.