Iran and world powers on Saturday battled to break the deadlock over Tehran's nuclear drive, extending talks into the evening after a day of exhausting diplomacy.
Officials from both sides were tight-lipped over whether any progress had been made in the talks in Kazakhstan but discussions continued longer than expected.
So far discussions have failed to resolve the main issue of whether Iran will accept limits on its nuclear programme in return for some relief on the sanctions that have hurt the Islamic Republic's economy in the past two years.
The world powers - comprised of the five permanent UN Security Council members and Germany and known collectively as the P5+1 - are represented by EU foreign policy chief Catherine Ashton.
Iran's team is led by top nuclear negotiator Saeed Jalili who has until now held out little hope of concessions from Tehran.
An Iranian official close to the negotiations in the Kazakh city of Almaty said Tehran submitted a "detailed proposal" on Saturday that set off the day's negotiations.
But sources added that the parties still could not agree on details as well as the vital subject of where and when to meet again.
As well as bilateral discussions, the two sides held a plenary meeting in the morning, then continued in the afternoon. Another plenary session took place in the evening, officials said.
The two sides had held an indecisive first day of meeting on Friday that ended with only an agreement to meet again and Western officials admitting the positions were still far apart.
Ashton started Saturday by meeting Jalili in the hope of establishing whether Tehran's position had shifted from its tough demands of the previous day.
"During Ms Ashton and Dr Saeed Jalili's meeting this morning the latest situation of the negotiations and different aspects of each side's stances were discussed in detail," said an Iranian official.
Both sides acknowledge differences despite growing Western fears about the possible military dimensions of Iran's nuclear programme.
Iran insists on international recognition of its asserted "right" to enrich uranium and wants that condition to be a part of any deal.
The world powers on the other hand say the onus is on Iran to take the first step to guarantee its nuclear programme is and has been exclusively peaceful.
They insist on Tehran ending enrichment to high levels and verifiably suspending operations at the Fordo mountain bunker where such activity takes place before recognising Iran's nuclear rights to less threatening activities.
Western officials had expressed puzzlement at Iran's reaction after the first day of talks but it was not clear if the second day was going any better.
"We had a long and substantial discussion on the issues, but we remain a long way apart on the substance," a Western official said after Friday's talks.
Iran in particular wants to see an end to biting US and EU sanctions that limit the Islamic republic's international banking transactions and cut the amount of cash it can get for the oil it still manages to sell abroad. The Islamic republic is also subject to separate UN sanctions.
Iran has reportedly only been offered the right to deal in some precious metals and perform small financial transactions now prohibited by the international sanctions. Tehran says it is being asked too much for too little in return.
The P5+1 grouping is especially worried about Iran's enrichment to levels of up to 20 percent and wants the Islamic republic to ship out the part of its 20-percent enriched uranium not converted into powder for reactor fuel.
Iran denies it is developing the atomic bomb and argues that it requires a nuclear programme solely for peaceful medical and energy needs.
However it has repeatedly stalled in talks with the UN nuclear watchdog which wants expanded inspections of Iran's programme to address suspicions of military-related work.