US President Barack Obama will nominate Solicitor-General Elena Kagan to the Supreme Court, US media reports say.
The White House has not yet commented, but Mr Obama is scheduled to announce his choice at 1000 (1400 GMT).
If confirmed, she would be the youngest member and third woman on the current court as well as the first justice in many years not to have been a judge.
The 50-year-old former dean of Harvard Law School has spent much of her professional life in academia.
Early in her career she was a clerk for a US Court of Appeals judge and later for former Justice Thurgood Marshall. And like Mr Obama, she worked on the prestigious Harvard Law Review as a student.
The president was forced to choose a nominee due to the retirement of one of the Supreme Court’s leading liberals, John Paul Stevens.