WASHINGTON — The woman who has accused President Trump’s Supreme Court nominee of sexual assault all but ruled out appearing at an extraordinary Senate hearing scheduled for next week to hear her allegations, insisting on Tuesday that the F.B.I. investigate first.

Speaking through lawyers, Christine Blasey Ford said she would cooperate with the Senate Judiciary Committee and left open the possibility of testifying later about her allegations against Judge Brett M. Kavanaugh. But echoing Senate Democrats, she said an investigation should be “the first step” before she is put “on national television to relive this traumatic and harrowing incident.”