ISTANBUL - Iran and world powers have a rare chance on Saturday to halt a downward diplomatic spiral over Tehran's nuclear programme and ease fears of a new Middle East war when they resume talks, but diplomats warn against expecting quick results.
The negotiations in Istanbul, the first between Iran and the six powers in 15 months, are unlikely to yield any major breakthrough but Western diplomats hope at last to see readiness from Tehran to start to discuss issues of substance.
That, they say, would mark a big change in Iran's attitude from the last meeting when it refused even to talk about its nuclear programme and could be enough for scheduling a second round of talks next month, perhaps in Baghdad.
Such an outcome could, at least for the time being, dampen persistent speculation that Israel might launch military strikes on Iranian nuclear sites to prevent its enemy from obtaining atomic arms.
Both sides say they are ready at the meeting, the start of which was delayed and is now due at around 11 a.m (0800 GMT), to work towards resolving the deepening dispute over the nuclear programme which Iran says has purely peaceful purposes.
"For their own reasons, each side wants to give diplomacy a chance at this point, to start a process rather than to force a quick fix," said analyst Michael Adler at the Woodrow Wilson International Center for Scholars.
Iran must show in Istanbul that it is willing to enter "serious engagement", one senior diplomat said, suggesting Saturday's discussions were unlikely to go into detailed issues.
"My tip is to set your sights low," the diplomat said. "It is not part of our game plan for tomorrow to lay out a long list of specific demands and conditions. They know what we think about all these things."
Iran says it will propose "new initiatives" in Istanbul, but it is unclear whether this means it is now prepared to discuss curbs to its uranium enrichment programme, which the West suspects has military links.
"Iran is sending signals they want a serious and constructive meeting," another diplomat said before the meeting between Iran and the United States, France, Russia, China, Germany and Britain and their main representative, European Union foreign policy chief Catherine Ashton.
The West accuses Iran of seeking 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. Iran has threatened to retaliate for any attack by closing a major oil shipping route.
Ashton and Iranian chief nuclear negotiator Saeed Jalili had a three-hour dinner on Friday which a diplomat said passed in a "friendly atmosphere", but he said discussions did not focus on the nuclear issue.