Updated

Iran and six world powers have tentatively decided to adjourn their nuclear talks early but plan to extend them past the July 20 target date for a deal, diplomats said Wednesday.

Both sides had been prepared to talk until Sunday, the informal deadline for the negotiations. But two diplomats have told The Associated Press the talks will probably wind down early, because significant differences won't be bridged by Sunday.

The diplomats demanded anonymity Wednesday because they were not authorized to divulge confidential information. One said both sides were against going on because they did not want to give an impression that negotiations were desperately looking for a deadline solution.

The talks aim to result in a deal that curbs Iran's atomic programs in exchange for an end to the nuclear-related economic sanctions on the Islamic Republic.

U.S. Secretary of State John Kerry spoke of "very real gaps" Tuesday after two days of meetings with Iranian Foreign Minister Mohammad Javad Zarif.

The main dispute is over uranium enrichment, which can make both reactor fuel and the fissile core of nuclear warheads.

Iran says it does not want such arms. Up to last week it insisted being allowed to expand its enrichment program over the next eight years to a level that would need about 190,000 current model centrifuges.

It now has about 20,000 centrifuges, with half of them operating. Iranian officials have recently signaled they are ready to freeze that number for now. But Kerry said Tuesday that Washington has made it "crystal clear" that even 10,000 are too many.