World powers sought a response from Iran Friday over a proposal for ending the decade-long nuclear crisis, even as the Islamic republic struck a tough line over its right to enrich uranium.
The world powers will be assessing whether Iran is ready to accept a series of demands that the powers presented at the last such negotiations at the same venue in Kazakhstan in February.
In the first round of an expected two days of talks in the mountain city of Almaty, Iran said chief negotiator Saeed Jalili has presented proposals of his own, in a scenario all too familiar from years of stalled diplomacy.
EU foreign policy chief Catherine Ashton, who represents the world powers, had said going into the talks that she hoped Iran would make a "considered, balanced and well-thought out response to try and reach an agreement on how we move forward."
Jalili's deputy Ali Bagheri said Iran presented its own counter-proposal but refused to specify whether it had actually presented a firm response to the powers' plan.
"At this morning's meeting, his excellency Dr. Jalili presented specific plans and proposals for starting a new round of cooperation between Iran" and the world powers, Bagheri told reporters shortly after the first of what are expected to be several plenary sessions wrapped up.
The last meeting in February ended with unusual expressions of cautious optimism from both sides. Iran described those negotiations as "positive" while the world powers more cooly called them "useful".
But Jalili defiantly indicated going into Friday's session that Tehran had no intention of giving ground on the most important concession demanded by the West.
He told the six powers -- comprised of the five permanent UN Security Council members and Germany and known collectively as the P5+1 -- that Iran demanded an immediate recognition of his country's right to enrich uranium.
"We think that they can open up tomorrow's (Friday's) talks with one phrase -- and that is to accept Iran's right, particularly its right to enrich," Jalili said in a speech Thursday at an Almaty university.
The demand is inherently objectionable to the powers because Iran is prohibited from enriching uranium by the United Nations and is heavily sanctioned for its secretive work.
Jalili also appeared to downplay the chances of his one-on-one meeting with chief US negotiator Wendy Sherman -- talks Washington has been seeking for years.
"What our nation is expecting is for the US to correct its behaviour, and not just in words, and tomorrow in Almaty they are in for another test," said Jalili.
An EU spokesman said decisions about bilateral meetings would be made as the talks progressed and refused to speculate about the reported possibility of dinner talks Friday between Jalili and Ashton.
Failure to strike a compromise could prove costly to both sides. A possible war would likely see a global spike in oil prices and draw in other regional powers at an already unstable time in the Middle East.
Israeli Prime Minister Benjamin Netanyahu for one warned this week that "we cannot allow" the talks to drag on indefinitely while Iran continues to pursue enrichment.
The P5+1 grouping is particularly concerned about Iran's enrichment to levels of up to 20 percent and the Fordo fortified bunker where such 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. Teheran has said that it was being asked to do too much for too little in return.
Yet UN Secretary General Ban Ki-moon said in Madrid it would be on the Iranian side to prove that its "nuclear development program is for peaceful purposes".