LONDON (Reuters) - Former U.S. President Jimmy Carter said on Sunday he expects Democratic superdelegates to reveal their choice for presidential nominee soon after the final primary in June and that Hillary Clinton will then have to quit the race.

In an interview with Sky News, Carter said he did not think Clinton was achieving anything by staying in the fight.

"I think not. But of course she has the perfect right to do so," he said while attending a literary festival in Britain.

"I'm a superdelegate ... I think a lot of the superdelegates will make a decision quite, announced quite rapidly, after the final primary on June 3," he told Sky News.

"I have not yet announced publicly, but I think at that point it will be time for her to give it up," Carter said.

Democratic presidential candidate Barack Obama is seen as front-runner. He holds a nearly insurmountable lead in delegates to the party's August nominating convention after months of contests that began in January.

Clinton has refused to quit until the last votes are cast and counted and the Democratic nominee is likely to be decided by the nearly 800 "superdelegates" -- members of Congress and other party insiders -- free to vote for whomever they want.

The Democratic candidates need 2,026 delegates to be nominated to run against Republican John McCain in the November 4 U.S. presidential election.

According to estimates by MSNBC, Obama now has 1,954 while Clinton has 1,783. There are 86 delegates left to be chosen in the state-by-state contests.

(Editing by Catherine Evans)