President Donald Trump's conservative pick for the Supreme Court Brett Kavanaugh denied Friday involvement in an alleged sexual assault on a woman while they were in high school in the 1980s.

In a statement released to US media, Kavanaugh rejected the woman's claim, made in a letter to the Democrats vetting his nomination, that he tried to force himself on her during a party.

"I categorically and unequivocally deny this allegation. I did not do this back in high school or at any time," Kavanaugh said in the statement.

The allegation came just one week before the Senate Judiciary Committee is to vote on his nomination. If approved by the committee and the whole Senate, as expected, Kavanaugh is likely to decidedly tilt the court to the conservatives for years to come.

According to an account in The New Yorker, the incident happened while Kavanaugh, now 53, attended the elite Georgetown Preparatory Catholic all-boys high school in suburban Washington.

The woman, from a nearby high school, was allegedly at a party where the youths were drinking alcohol.

In a room with the woman, Kavanaugh and another male teen turned up the music and placed their hands over her mouth so that no one could hear, and Kavanaugh "attempted to force himself on her," The New Yorker reported, citing the woman's account.

She struggled with them and escaped, the account said.

Kavanaugh was quickly defended by friends and acquaintances from the time who cast doubts on the alleged incident. A group of 65 women signed a letter attesting to his character.