US Supreme Court justice Ruth Bader Ginsburg said her predecessors may have mistimed the milestone 1973 Roe v Wade case that legalised abortion nationwide.

"It's not that the judgment was wrong, but it moved too far too fast," Ms Ginsburg told a symposium at Columbia Law School marking the 40th anniversary of her joining the faculty.

At the time of Roe, abortion was legal in four states, allowed under limited circumstances in some others, and outlawed under nearly all circumstances in most states, including Texas - where the case originated.

Alluding to the persisting abortion debate, Ms Ginsburg said the justices of 1973 could have delayed hearing Roe while the state-by-state process evolved.

Or they could have struck down just the Texas law without legalising the procedure nationwide.