Iran on Sunday said that possible talks between the "P5+1" group and Iran, on the latter's nuclear program, may take place in Istanbul, claiming that the Turkish foreign minister and EU foreign policy chief Catherine Ashton have agreed to the venue.Iranian Foreign Minister Ali Salehi said Tehran is waiting for a response to a letter sent to the European Union representative last week, semi-official Iranian news agency Mehr reported.Ashton, who handles contact with Iran on behalf of the "P5+1" group comprised of the United States, Britain, France, Russia, China and Germany, said the letter showed "a potential possibility that Iran may be ready to start talks."Clinton, however, said the Iranian letter "appeared to acknowledge and accept" the western countries' longstanding condition that any talks begin with a discussion of its nuclear program."We must be assured that, if we make a decision to go forward, we see a sustained effort by Iran to come to the table, to work until we have reached an outcome that has Iran coming back into compliance with their international obligations," Clinton said.Reuters contributed to this report.The letter to Ashton, which was obtained by Reuters on Thursday, proposed resuming the stalled talks and said Tehran would have "new initiatives" to bring to the table.But the brief letter, which responded to a letter Ashton sent to her Iranian counterpart in October, offered no specific proposals, leaving a question mark over Tehran's willingness to enter substantive negotiations on its nuclear work.Following a meeting Friday, Ashton and US Secretary of State Hillary Clinton told reporters that Iran's recent letter to Ashton might mark a step forward."We think this is an important step and we welcome the letter," Clinton said in a joint meeting with Ashton. She stressed that the major powers were still reviewing their formal response to Tehran's offer.