WASHINGTON — A secretive letter shared with authorities by the senior Democrat on the Senate Judiciary Committee charges that a teenage Brett M. Kavanaugh and a male friend trapped a teenage girl in a bedroom during a party and tried to assault her, according to three people familiar with the contents of the letter.
According to the letter, Mr. Kavanaugh, then a student at Georgetown Preparatory School in suburban Washington and now President Trump’s Supreme Court nominee, had been drinking at a social gathering when he and the male friend took the teenage girl into a bedroom. The door was locked, and she was thrown on the bed, the letter says. Mr. Kavanaugh then got on top of the teenager and put a hand over her mouth, as the music was turned up, according to the account.
But the young woman was able to extricate herself and leave the room before anything else occurred, the letter says.
The woman considered the incident an assault. She has declined to be publicly identified, and asked Senator Dianne Feinstein, the top Democrat on the Judiciary Committee, not to publicize the letter.
The episode took place more than 30 years ago, when all three individuals involved were minors. The New York Times has not seen the letter, but its contents were described by the three people.
In a statement shared by the White House, Mr. Kavanaugh said the charges were false.
“I categorically and unequivocally deny this allegation,” he said. “I did not do this back in high school or at any time.”
As of Friday morning, senators were still planning to move ahead with Mr. Kavanaugh’s confirmation. The Judiciary Committee is scheduled to hold a key vote to advance the nomination next Thursday, and Republican leaders hope to hold a final vote of the full Senate before the end of September to allow Mr. Kavanaugh to be seated before the start of the Supreme Court’s fall term.
On Thursday, the White House all but accused Democrats of playing dirty, withholding mysterious information until the eve of Mr. Kavanaugh’s confirmation in a last-ditch effort to derail a nominee they have always opposed.
“Senator Schumer promised to ‘oppose Judge Kavanaugh’s nomination with everything I have,’ and it appears he is delivering with this 11th-hour attempt to delay his confirmation,” said Kerri Kupec, a White House spokeswoman, referring to the top Senate Democrat, Chuck Schumer. Aides to Mr. Schumer said he had not seen the letter.
The letter arrived on Capitol Hill in July, first to the office of Representative Anna Eshoo, Democrat of California. Ms. Eshoo ultimately shared it with Ms. Feinstein, who had held close its contents until Wednesday, when swirling rumors on Capitol Hill and in the news media persuaded her to share its contents — but not the letter itself — with fellow Democratic senators on the committee.
Several of those senators advised Ms. Feinstein to at least share the letter with law enforcement authorities, and on Thursday she announced in a cryptic statement that she had sent “information from an individual concerning the nomination of Brett Kavanaugh to the Supreme Court” to the authorities.
The F.B.I. has not opened a criminal investigation into the matter, but added the letter to Judge Kavanaugh’s background file. That updated file was shared with the White House on Thursday and then sent to Capitol Hill, where it will be kept in the office of Senator Charles E. Grassley of Iowa, the Republican chairman of the Judiciary Committee.
With speculation about the letter’s contents circulating, Mr. Grassley on Friday released a different letter, sent to him and to Ms. Feinstein and signed by 65 women who say they knew Judge Kavanaugh while in high school.
“Through the more than 35 years we have known him, Brett has stood out for his friendship, character, and integrity,” the women wrote. “In particular, he has always treated women with decency and respect. That was true when he was in high school, and it has remained true to this day.”