VIENNA — Iran nuclear talks stalled Friday, casting a shadow on earlier advances and denting hopes that Tehran and six world powers will meet a July 20 target date for a deal meant to curb Iran’s atomic program while ending sanctions on the Islamic Republic.
Deputy Iranian Foreign Minister Abbas Araghchi acknowledged the meeting made ‘‘no progress’’ in its ambitious goal of starting to draft an agreement meant to ease a decade of Western distrust about Tehran’s nuclear agenda in exchange for sanctions relief.
In that, ‘‘we failed,’’ he told reporters. But while saying he was disappointed, he insisted that the result of the three-day talks that ended Friday represented no more than a setback at this point in continuing attempts to reach a deal.
A senior US official who demanded anonymity said there was ‘‘great difficulty’’ in trying to move toward common positions and spoke of ‘‘significant’’ differences. Both Araghchi and the official said further meetings were planned in June, but no dates were announced.
The failure to advance diminished a sense of optimism that had been growing since talks began Feb. 18. But while diplomats had spoken of some progress before the three-day round that ended Friday, they had also warned of difficult talks ahead on some issues, such as Iran’s enrichment program.
In Jerusalem on Friday, Defense Secretary Chuck Hagel pledged to Israeli leaders that the United States ‘‘will do what we must’’ to prevent a nuclear-armed Iran, the Jewish state’s greatest fear.
Hagel made the public pledge after talks with Prime Minister Benjamin Netanyahu. ‘‘I want to assure you of the United States’ commitment to ensuring Iran does not get a nuclear weapon — and that America will do what we must to live up to that commitment,’’ Hagel said.
Standing beside Hagel, Netanyahu said, ‘‘We've been saying all along that Iran is trying to pull the wool over the eyes of the international community.’’ He urged a clear and firm stand by world powers.
Iran says it has no interest in nuclear arms, and wants to enrich only to make reactor fuel. But because the technology can also create weapons-grade uranium for warheads, Washington and its allies want strict constraints on its size and scope.
Araghchi said differences remained on more than a dozen issues and a Western official with detailed knowledge of the talks said enrichment was among the most divisive topic.
Iran’s nuclear chief, Ali Akbar Salehi, has said publicly that Tehran needs up to 100,000 centrifuges — the enriching machines — for a future nuclear network.
That’s about five times as many as the centrifuges Iran now has standing but idle, 10 times that of the machines actually enriching — and much more than the few thousand that diplomats say the United States and its allies are prepared to allow.
Related differences focus on length of constraints on enrichment and other nuclear activities that could be proliferation-relevant. The diplomats say the United States and other Western countries want decade-long limits, whereas Tehran is pushing only for a few years before all restrictions are lifted.