There was some relief that Iran was ready to continue, as diplomats expressed concern that talks could have collapsed on the first day as both sides dug in around old positions. 

The West suspects that Iran plans to develop a nuclear weapon and negotiators went into the Istanbul meeting with low expectations for any breakthrough in the eight-year-old stand-off. Tehran says its atomic energy program is peaceful. 

EU foreign policy chief Catherine Ashton is the lead negotiator for the big powers - the United States, Britain, France, Russia, China and Gernamy. 

Iran's nuclear negotiator Saeed Jalili also met separately with heads of the Russian and Chinese delegations, but it was uncertain whether he would agree to meet Under-Secretary for Political Affairs Bill Burns, the head of the US team. 

Burns and Jalili met on the sidelines of an earlier round of talks in Geneva in 2009, but such contacts have been rarely confirmed by the Iranian side and usually have taken place behind the scenes since the fall of the US-backed shah in Iran in 1979. 

Early on during the sessions on January 22, an Iranian delegate said Iran refused to discuss any suspension of its uranium enrichment activities during the Istanbul talks.