A member of one of the delegations meeting with Iran told The Associated Press the plan offered reductions in both the levels of uranium enrichment being conducted by Iran and the number of centrifuges doing the enrichment a key demand of the six powers. He demanded anonymity because he was not authorized to divulge details.
Iran's state TV, which closely reflects government views, said Tehran offered to discuss uranium enrichment levels. The report also said Iran proposed adopting the additional protocols of the U.N.'s nuclear treaty effectively opening its nuclear facilities to wider inspection and monitoring if the West recognizes Iran's right to enrich uranium.
The Iranian presentation was followed in the afternoon by what European Union spokesman Michael Mann said were very detailed technical talks "for the first time." State Department spokeswoman Jen Psaki repeated the same phrase, saying that while it wasn't "a breakthrough at this stage ... it certainly is positive that there was enough information to have technical discussions."
"They've come forward with something this morning, but we need to work harder on it to get down to the nitty gritty," Mann told reporters. Both he and Psaki said the talks would continue Wednesday.
Araghchi was also upbeat, describing the afternoon session as "positive and constructive," on the website of Iranian state television. He said the six powers the United States, Russia, China, Britain, France and Germany asked for details and discussed explanations offered by Iranian negotiators.
Iran's version of success is for painful international sanctions to be lifted in exchange for possible concessions it had been previously unwilling to consider, such as increased monitoring and scaling back of uranium enrichment a potential path to nuclear arms and the centerpiece of the impasse with the West.
International talks designed to reduce fears that Iran may make such arms have been stalled for most of their 10-year history, with Tehran insisting it has no interest in weapons production, while resisting both enticements and sanctions designed to force it into ending uranium enrichment and other activities that could be used to make weapons.
But the talks appear now to be driven by the new wind generated since reformist President Hassan Rouhani took office in September.
Senior Iranian officials have expressed readiness to modify their rigid stance since then, and the Geneva talks were seen as the first real test of Tehran's willingness to move from soothing words to concrete and verifiable actions.
At the end of the hour-long PowerPoint presentation, Araghchi described his country's proposal as a potential breakthrough. Alluding to the international pressure over Iran's nuclear program that has driven the country into near-pariah status, he said: "We no longer want to walk in the dark and uncertainty and have doubts about the future."
Iran's uranium enrichment program is at the core of the world powers' concerns. Iran now has more than 10,000 centrifuges churning out enriched uranium, which can be used either to power reactors or to make a nuclear bomb. Iran has long insisted it does not want nuclear arms a claim the U.S. and its allies have been skeptical about but has resisted international attempts to verify its aims.
Back pains suffered by Zarif, Iran's foreign minister and chief negotiator, threatened to complicate the talks. However, Mann said the pains did not stop Zarif from having a "cordial" dinner Monday evening with Catherine Ashton, the top EU diplomat convening the talks.
Araghchi said Zarif was "suffering a lot," although he intended to stay in Geneva until the talks ended. He was later seen leaving the service entrance of his upscale hotel in a wheelchair, with security guards wheeling him into a van.
Of the tons of enriched uranium in Iran's stockpile, most is enriched to under 5 percent a level that needs weeks of further enrichment to turn into weapons-level uranium. But it also has nearly 200 kilograms (440 pounds) of 20 percent-enriched uranium, a form that can be quickly upgraded for weapons use, according to the U.N's atomic agency, which keeps tabs on Iran's nuclear activities. That is close to but still below what is needed for one nuclear weapon.
No final deal is expected at the two-day session, but it potentially could be the launching pad for a deal that has proven elusive since negotiations began in 2003, while reducing the specter of armed conflict in the Mideast.
Israeli Prime Minister Benjamin Netanyahu claims that Iran's new leadership is trying to use the negotiations to trick the world into easing sanctions without making any significant concessions. Netanyahu says a nuclear-armed Iran is unacceptable and has repeatedly threatened to attack Iran, unilaterally if necessary, if diplomacy fails to curb the nuclear program.
Netanyahu appeared to make a new threat against Iran on Tuesday when, during a memorial service marking the 40th anniversary of the 1973 Arab-Israeli war, he said a lesson of that conflict is that "pre-emptive strikes must not be ruled out."
One immediate change from previous talks was the choice of language. They were held in English, unlike previous rounds under Mahmoud Ahmadinejad, Rouhani's hard-line predecessor, when English and Farsi were spoken and translations provided of the exchange.