ISTANBUL (Reuters) - Talks between Iran and six world powers resumed in Turkey on Saturday after a 15-month gap, as delegates sought to find ways of resolving a dispute over Tehran's nuclear programme and easing fears of a new Middle East war.
One diplomat described the atmosphere as "completely different" from that of previous meetings, as Western delegates watched out for signs that Iran was ready to engage seriously after more than a year of threats and accusations.
The talks are unlikely to yield any major breakthrough but diplomats believe a serious commitment from Iran could be enough to schedule another round of talks for next month and start discussing issues at the heart of the dispute.
"The atmosphere is constructive, the conversation is businesslike. As of the moment, things are going well," Deputy Foreign Minister Sergei Ryabkov, who is leading the Russian delegation, was quoted as saying by Interfax news agency.
The West accuses Iran of trying to develop a nuclear weapons capability. Israel - believed to be the only Middle East state with an atomic arsenal - sees Iran's atomic plans as a threat to its existence and has threatened military action.
Iran says its programme is peaceful and has threatened to retaliate for any attack by closing a major oil shipping route.
Tehran agreed to resume talks with the five permanent members of the U.N. Security Council plus Germany after more than a year marked by escalating rhetoric and tensions.
The United States and Israel have not ruled out military action to destroy Iran's nuclear sites.
In the run-up to the Turkey meeting, Western diplomats had said they hoped for enough progress to be able to schedule a new round of negotiations, possibly in Baghdad, next month.
The morning round of talks was "completely different" from the previous meeting 15 months ago and Iranian chief nuclear negotiator Saeed Jalili had not stated the kind of preconditions that he did in the last meeting in early 2011, a diplomat said.
"He seems to have come with an objective to get into a process which is a serious process," the envoy said. "I would say it has been a useful morning's work."
Iran says it will propose "new initiatives" in Istanbul, though it is unclear whether it is now prepared to discuss curbs to its enrichment programme. But the atmosphere was positive.
"They met in a constructive atmosphere," said Michael Mann, a spokesman for EU foreign policy chief Catherine Ashton, after the morning session of talks. "We had a positive feeling that they did want to engage."
Ashton, who is the main representative of the United States, France, Russia, China, Germany and Britain at the talks, added: "What we are here to do is to find ways in which we can build confidence between us and ways in which we can demonstrate that Iran is moving away from a nuclear weapons programme."
Iran's ISNA news agency reported a U.S. envoy had asked for a meeting with Iran's chief nuclear negotiator and that Jalili had accepted, but another news agency, Fars, later denied that.
One diplomat, asked about the ISNA report, said it was not clear whether there would be any bilateral meetings.
The United States cut diplomatic ties with Iran in 1980 after Iranian students held 52 American diplomats hostage for 444 days, and the two sides have held very rare one-to-one meetings since then.
Iran, one of the world's largest oil producers, says its nuclear programme has solely peaceful objectives - to generate electricity and produce medical isotopes for cancer patients.
But its refusal to halt nuclear work which can have both civilian and military uses has been punished with intensifying U.S. and EU sanctions against its lifeblood oil exports.
"Given that oil revenue accounts for over half of government income, the budget will be under significant strain this year as oil exports fall as a result of sanctions and oil production is cut back by Iran as its pool of buyers begins to shrink," said Dubai-based independent analyst Mohammed Shakeel.
Western officials have made clear their immediate priority is to persuade Tehran to cease the higher-grade uranium enrichment it began in 2010. It has since expanded that work, shortening the time it would need for any weapons "break-out".
Iran has signalled some flexibility over limiting its uranium enrichment to a fissile purity of 20 percent - compared with the 5 percent level required for nuclear power plants - but also suggests it is not ready to do so yet.
Additional reporting by Justyna Pawlak in Istanbul, Zahra Hosseinian in Zurich and Marcus George in Dubai; Writing by Maria Golovnina; Editing by Tim Pearce