Iran went into talks with world powers in apparently uncompromising mood Thursday by demanding the immediate recognition of its right to enrich uranium and dismissing the chances of direct talks with the United States.
The powers themselves expressed cautious optimism as each side settled in for two days of meetings that start Friday on Iran's nuclear programme in the Kazakh city of Almaty -- the fifth such talks in two years.
Iran's chief nuclear negotiator pronounced the last negotiations at the same venue "positive" and but said the powers -- comprised of the five permanent UN Security Council members and Germany and known as the P5+1 -- has to agree to its key demand in the decade-old dispute.
"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," Saeed Jalili said in a speech at an Almaty university ahead of the negotiations.
"We hope that in Almaty, they do not repeat the bitter experience they have gone through in the 34 years of our revolution and that they make the right conclusion this spring," he said referring to the 1979 Islamic revolution that ousted the shah.
The demand is inherently objectionable to world 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 in just words, and tomorrow in Almaty they are in for another test," said Jalili.
"Those who come to negotiations should come with logic and not threats, saying that all the options are on the table. This is contrary to common sense."
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.
The powers 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 offer 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. The Islamic Republic has already called this approach unbalanced.
But a senior US administration official said the offer on the table now was "balanced and very fair."
"It is impossible to predict the results, but we will stay very engaged with Iran," said the US official.
"We hope Iran comes prepared and makes a concrete and substantive response" to a package proposed in February.
The official refused to speculate about what would happen should Iran not accept the proposal's terms or present its own unacceptable counter-offer.
"I would hope that we are not at any last chance," said the official.
"I think if we're not sure about how much we've gotten and whether we have gotten enough, we'll go back and consult with capitals before we reach any ultimate conclusion here. So I think we have time and space to consider what we hear."
EU foreign policy chief Catherine Ashton -- Jalili's counterpart at the Almaty talks -- herself said that she was going into the meeting with her usual "cautious optimism".