Two days of talks between six world powers and Iran, aimed at persuading the Islamic Republic to rein in its nuclear programme, concluded to day, a Western diplomat said.
EU foreign policy chief Catherine Ashton, who led delegations from the US, Britain, France, Russia, China and Germany was due to address a news conference. Her Iranian counterpart Saeed Jalili was also expected to hold a news conference.
The west suspects Iran plans to develop nuclear weapons while Tehran says its atomic energy programme is peaceful.
The standoff has dragged on for eight years. There have been scant signs of progress during the talks.
Progress on the first day was thin, with Iran insisting on preconditions, including the lifting of sanctions and recognition of its right to enrich uranium. It blamed the big powers for the impasse.
"The outcome of these talks should pave the ground for the next talks ... Unfortunately the other party has no clear and convincing agenda for talks and they just want to hold talks," said Abolfazl Zohrevand, an aide to Iran's chief negotiator Mr Jalili.
"Today we want some tangible ways to be found for active cooperation in various fields."
A Western diplomat at the talks said the powers hoped for signs that Iran wanted to engage seriously this time, rather than set unacceptable preconditions.
"Iran's preconditions - asking us to accept Iran having a full fuel cycle and lift sanctions upfront before any progress - were summarily rejected," he said.
Negotiators went into the Istanbul meeting with low expectations of a breakthrough in a meeting that is a follow-up to one held in Geneva last month, which was the first time the two sides had met in more than a year.
This morning, Iran said it had rejected a proposal for a bilateral meeting with the United States, saying it was not necessary within the context of the Istanbul nuclear talks.
"But there is no need to hold such talks if it is not about the nuclear meeting in Istanbul," Zohrevand told Iran's Arabic-language Al Alam television news channel.
Since the fall of the US-backed shah in 1979, any contacts between the Islamic Republic and the United States have usually taken place behind the scenes, and were rarely confirmed by the Iranian side.
Reuters