Iran and world powers on Saturday meet for a second and final day of a new round of talks aimed at breaking a decade-old deadlock over the Islamic state's disputed nuclear programme, with time slowly running out on a solution.
The two sides held a tense day of negotiation in the Kazakh city of Almaty on Friday that ended with only an agreement to meet again.
The sides failed to resolve the main issue on the table: Iran's willingness to accept some watered-down demands concerning its nuclear programme in return for relief of sanctions, which have crippled the Islamic republic's economy in the past two years.
Iran resolutely insists on international recognition of its right to enrich uranium and wants that condition be a part of any deal.
The world powers on the other hand say the onus is on Iran to take the first step, and insist on it ending enrichment to high levels and shutting down a bunker location at which this activity goes on before any recognition for Iran's nuclear rights are granted.
The talks concluded on Friday after two plenary sessions lasting a combined six hours with Iran answering a series of questions about its list of demands.
A Western official said the two sides still had strongly differing visions of ways to solve the dispute.
"We had a long and substantial discussion on the issues, but we remain a long way apart on the substance," one Western official said after Friday's talks.
"We are now evaluating the situation and will meet again tomorrow (Saturday)."
Russian negotiator Sergei Ryabkov summed up the day by saying that the difficulty at the talks proved their seriousness.
"The answers prompted more questions," Russian news agencies quoted Ryabkov as saying.
"But this proves that these talks are serious."
Iran in particular wants to see an end to the biting sanctions imposed by the European Union and the United States that limit the Islamic republic's shipping activities and cut the amount of oil it can export.
The powers -- comprised of the five permanent UN Security Council members and Germany and known collectively as the P5+1 -- argue that such a sweeping gesture does not correspond with their persistent concerns over the possible military dimensions of Iran's work.
The P5+1 grouping is particularly worried about Iran's enrichment to levels of up to 20 percent and the Fordo fortified bunker where this activity is conducted.
They also want Iran to ship out its existing stockpile of 20-percent enriched material.
Iran denies it is developing the atomic bomb and argues that it needs its nuclear programme for peaceful medical and energy needs.
The powers proposed in February that Iran shutter the Fordo reactor and in exchange receive small concessions that hold out the hope of greater ones if it made a bigger step.
Iran has reportedly been offered the right to deal in some precious metals and perform small financial transactions now prohibited by international sanctions. Tehran says it is being asked too much for too little in return.