ALMATY, Kazakhstan — Negotiations over Iran's disputed nuclear program broke off Saturday with scant signs of progress, much less an agreement on tighter controls demanded by six world powers in exchange for some easing of sanctions that have a stranglehold on the Iranian economy.
The failure to reach any accord was a stark but not surprising setback in a decadelong standoff over Iran's nuclear ambitions. While the talks have been complicated by the Iranian presidential election just 10 weeks away, officials said the sides remained divided by fundamental disagreements, none of which are new.
Catherine Ashton, the European Union's foreign policy chief, who led the talks for the six powers, said that after two days of "long and intense discussions," the sides "remain far apart on the substance."
No future negotiations were announced, and Ashton said she would be "in touch very soon" with the top Iranian negotiator, Saeed Jalili, "in order to see how to go forward."
Jalili offered a sharply different summary, saying at a briefing that the next move was up to the big powers, and that they needed more time to digest a new proposal from Iran. He said the proposal was largely based on a plan first put forward in Moscow in June and aimed at addressing some of the international community's concerns.
But he also adopted a strident tone in reiterating Iran's view that it has a right to enrich uranium for civilian purposes.
A senior U.S. official called Iran's demands unreasonable. The official spoke to the New York Times on the condition of anonymity, which has become the State Department's standard practice at the talks.
The official insisted that the Obama administration is still committed to achieving a diplomatic solution, but warned of sanctions should Iran fail to curb its nuclear program.
Britain also warned of tougher sanctions. "Iran's current position falls far short of what is needed to achieve a diplomatic breakthrough," Foreign Secretary William Hague said in a statement. He added: "We look to Iran to consider carefully whether it wants to continue on its current course, and face increasing pressure and isolation from the international community."
The futility of the talks was certain to arouse renewed alarm, particularly from Israel, which had tempered its repeated threats of a military strike against Iranian nuclear sites in deference to the diplomatic efforts.
"This failure was predictable," Yuval Steinitz, Israel's minister of strategic affairs, said in a statement. "Israel has already warned that the Iranians are exploiting the talks in order to play for time while making additional progress in enriching uranium for an atomic bomb." He added: "The time has come for the world to take a more assertive stand and make it unequivocally clear to the Iranians that the negotiations games have run their course."
The conclusion of the talks without agreement on even a modest confidence-building measure or the clear prospect of future talks was striking, given that all sides seemed to have incentives to keep the conversation going, and to avoid talk of military intervention.
The talks in Kazakhstan were the fifth round over the past year between Iran, the five permanent members of the U.N. Security Council — Britain, China, France, Russia and the United States — plus Germany.