World powers presented Iran with an updated offer during negotiations on its nuclear program in Almaty on Tuesday, and hope for "more detailed feedback" from the Iranian side when talks resume as scheduled on Wednesday, an EU spokesman said.
"We had a useful meeting today," Michael Mann, spokesman for European Union foreign policy chief Catherine Ashton, told reporters after the first day of the talks.
"Hopefully the Iranians will be able to reflect overnight and will come back and view our proposal positively," he said, declining to give details of the powers' proposal.
Western officials have said it includes an offer to ease sanctions on trade in gold and other precious metals if Iran agrees to halt its most sensitive nuclear activity, which the West suspects has a military dimension - something Iran denies.
Mann said the proposal by the six powers - the United States, Russia, China, France, Britain and Germany - had been discussed during Tuesday's talks, but he did not elaborate.
"The proposal was set out in a relatively clear fashion," he said. "The Iranians went away to consider our proposal (and) there were further discussions in the course of the afternoon and the evening ... the ball is in their court."
The talks in Kazakhstan were the first in eight months between Iran and the five permanent members of the U.N. Security Council plus Germany - the "P5+1" - on a decade-old dispute that threatens to trigger another war in the Middle East.
Iran has used the time since the last meeting in June to further expand activity that the West suspects is aimed at enabling it to build a nuclear bomb, something that Israel has suggested it will prevent by force if diplomacy fails.