Former president Donald Trump has reportedly used a slur often targeted at women to describe vice president Kamala Harris during at least two private conversations.
His campaign denies the accusations.
The New York Times cited two people who, on different occasions, heard Mr Trump call Ms Harris a “bitch”.
The people were granted anonymity to describe private discussions.
In response, Trump campaign spokesperson Steven Cheung said: “That is not language President Trump has used to describe Kamala and it’s not how the campaign would characterise her.”
Mr Trump, a Republican, has a history of making derogatory statements about women and his political opponents.
He has called Ms Harris, the Democrats’ presidential candidate, and other women, including 2016 Democratic nominee Hillary Clinton, “nasty”, and he bragged about grabbing women’s genitalia in the infamous “Access Hollywood” tape.
He called Carly Fiorina, one of his rivals for the Republican nomination in 2016, “horseface” during a campaign debate.
Last month, Mr Trump said falsely that Ms Harris, who is black and of Asian descent, has misled voters about her race.
Mr Trump has said that E Jean Carroll, a writer who accused him of raping her, was a “nut job” who invented “a fraudulent and false story” to sell a memoir.
A New York jury found Mr Trump liable for sexual abuse, but not rape, in a civil case filed by Ms Carroll.
Mr Trump has also directed disparaging comments toward men. He branded former rivals senator Marco Rubio of Florida “liddle Marco”, senator Ted Cruz of Texas “lyin’ Ted” and former governor Jeb Bush of Florida “low energy Jeb”.
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