Brett Kavanaugh has said he will "not be intimidated into withdrawing" his nomination for the Supreme Court after he was accused of sexual misconduct.
Mr Kavanaugh and his first accuser, university professor Christine Blasey Ford, are due to testify to the Senate judiciary committee on Thursday.
She has claimed he molested her when they were in their teens at a high school party in Maryland in 1982.
A second woman, Deborah Ramirez, has told The New Yorker that Mr Kavanaugh exposed himself to her in college.
Mr Kavanaugh, a District of Columbia appeals judge nominated by US President Donald Trump, has denied both allegations.
In a letter to the judiciary panel, he wrote: "These are smears, pure and simple."
He said that all of the witnesses identified by Dr Ford as being present at the party have said they have "no recollection of any such party happening" on the record to the committee.
It comes after Mr Trump publicly challenged Dr Ford's veracity, tweeting she should have reported her alleged assault sooner if it was as "bad as she says".
"Judge Kavanaugh is an outstanding person. I am with him all the way," he said as he arrived in New York to attend the UN general assembly, calling the allegations politically motivated.
I have no doubt that, if the attack on Dr. Ford was as bad as she says, charges would have been immediately filed with local Law Enforcement Authorities by either her or her loving parents. I ask that she bring those filings forward so that we can learn date, time, and place!
— Donald J. Trump (@realDonaldTrump) September 21, 2018
Social media users responded with fury to the president's comments with the trending hashtag #WhyIDidn'tReport.
On Monday, protesters staged a national #BelieveSurvivors walkout at their places of work in solidarity with Dr Ford and Ms Ramirez.
In his letter, Mr Kavanaugh called the allegations "grotesque and obvious character assassination" and added that they could dissuade others from entering public service.
He said that he "will not be intimidated into withdrawing from this process".
"The coordinated effort to destroy my good name will not drive me out."
On Saturday, Dr Ford agreed to appear before the Senate judiciary committee overseeing his nomination.
Her lawyers issued a statement on Sunday saying: "Despite actual threats to her safety and her life, Dr Ford believes it is important for senators to hear directly from her about the sexual assault committed against her."
The allegations from 36 years ago have put in jeopardy Mr Kavanaugh's chances of winning confirmation in a Senate narrowly controlled by Mr Trump's party.
More from US
Utah Senator Orrin Hatch said The New Yorker piece including the second allegation is a Democratic "smear campaign".
He said the judiciary committee should hear from Dr Ford and "then we should vote".