"I think a lot of the superdelegates will make a decision quite, announced quite rapidly, after the final primary on June 3," Carter said in an interview with Sky News in London. "I have not yet announced publicly, but I think at that point it will be time for her to give it up."
Carter said he didn't think Clinton was achieving anything by staying in the race but added "of course she has the perfect right to do so."
Though ahead in the delegate count with 1,975 to Clinton's 1,773, Obama, the Democratic front-runner, has still not yet won the nomination.
Whether or not it looks presumptuous, he is now campaigning not in primary states but general election states like Nevada, Colorado and New Mexico.