Only then would the most crippling sanctions on Iranian oil sales and financial transactions be rolled back.
"There are narrow gaps, but they are important gaps," British Foreign Secretary William Hague said about the drafting process. Iran's Fars news agency quotedAraghchi as saying "the dispute is over the wording" but he was unsure when a deal might be final.
An agreement would cap nearly a decade of inconclusive international efforts to halt Iran's expanding nuclear program. Iran insists its program is for peaceful purposes and not aimed at building nuclear weapons.
A deal would build on the momentum of the historic dialogue opened during September's annual U.N. gathering, which included a 15-minute phone conversation between President Barack Obama and Iran's new president, Hassan Rouhani, after three decades of U.S.-Iranian estrangement.
For the U.S. and its five partners, the chief concern is uranium enrichment.
Since it was revealed in 2003, Iran's enrichment program has grown from a few dozen enriching centrifuges to more than 18,000 installed and over 10,000 operating. The machines have produced tons of low-enriched uranium, which can be turned into weapons grade material.
Iran also has stockpiled almost 200 kilograms (440 pounds) of higher-enriched uranium in a form that can be converted more quickly to fissile warhead material than the low-enriched uranium. Its supply is nearly enough for one bomb.
Based on comments from diplomats, the talks on Saturday appear to have included ways Iran could retain some level of enrichment, although at a level far below what's need for weapons.
While saying they are ready for compromise, the Iranians are mindful of criticism from hard-liners back home who oppose dealings with the United States.
Statements on Saturday by senior Iranian negotiators appeared to be an attempt to defuse domestic opposition to a deal that skeptics see as surrendering their country's nuclear sovereignty.
"I assure Iranians enrichment will never stop," Iran's state TV quoted Foreign Minister Mohammad Abbas Zarif as saying. "Iran opposes any demands restricting its rights.'"
The Iranians also are holding out for maximum relief from economic sanctions. The United States and its partners want to relax sanctions in small, incremental steps during the six months of an interim agreement but not remove them entirely pending a final stage deal.
Issues were believed to include the level of sanctions relief and the future of a plutonium reactor under construction at Arak that the six want closed. Plutonium can also be used to make nuclear weapons.
With the talks already running two days over schedule, it was unclear whether the negotiations would continue Sunday. Kerry's spokeswoman, Jen Psaki, said he still planned to travel to London on Sunday for meetings on other Middle East issues.
Kerry and his counterparts from Russia, Britain, France, China and Germany joined the Geneva talks after Iranian Foreign Minister Mohammad Javad Zarif and top European Union diplomat Catherine Ashton reported progress on enrichment and other issues Friday.
Their participation raised speculation that an agreement was close an interpretation that the foreign ministers themselves sought to discourage.
"We're not here because things are necessarily finished," Britain's Hague told reporters. "We're here because they're difficult, and they remain difficult."
The U.S. administration has not confirmed details of what concessions on economic sanctions it might offer. But a member of Congress and legislative aides have said the White House was considering releasing about $6 billion to $10 billion in Iranian funds frozen in foreign banks.
Iran would also be allowed to sell petrochemicals and be supplied with auto parts to revive its car industry and exports of automobiles to parts of Asia. The aides and the member of Congress demanded anonymity because they weren't authorized to divulge the estimate publicly.
A senior U.S. official told reporters last week that Iran is losing $5 billion a month in lost oil sales alone and $120 billion in total from all sanctions since their imposition, although he did not give a time frame. The official demanded anonymity in keeping with rules established by the U.S. administration.
The U.S. administration is keen to keep rollbacks limited to placate influential members of U.S. Congress who argue that pressure has brought Iran to the negotiating table and cannot be relaxed until Tehran offers significant concessions.
- AP
