Talks between Iran and six world powers over its nuclear programme will continue for a second day.
Both sides appear to have come to the discussions in Almaty, Kazakhstan, with new ideas. Western officials have described the talks so far as "useful".
An EU official said: "We had a useful meeting today. Further discussions took place this evening. We have agreed to have another meeting tomorrow."
Western diplomats went to Almaty with what they described as a significant new proposal.
The world powers are offering Iran permission to resume its gold and precious metals trade as well as some international banking activity which are currently under sanctions.
But in exchange, Iran will have to limit sensitive uranium enrichment operations which the world powers fear could be used to make a nuclear bomb.
Iran would have to stop enriching uranium to 20% and shut down its controversial Fordo plant where such activity occurs, a Western official said.
An Iranian source said Tehran had come up with a counter-offer, whose final nature would be determined by terms posed by the so-called P5+1, the five permanent UN Security Council members - the UK, France, the US, Russia and China - and Germany.
But a source stressed "there was no question" of Tehran closing the Fordo plant where uranium is enriched to up to 20% - a level seen as being within technical reach of weapons-grade matter.
But Iran could envisage halting the enrichment of uranium to 20%, if all international sanctions against it were dropped, including UN Security Council measures, the source said.
"We have come here with a revised offer and we have come to engage with Iran in a meaningful way," EU foreign policy chief Baroness Ashton, who negotiates with Iran on behalf of the world powers, said in a statement.
She said the ambition was that "we see progress by the end of the meeting".
"It's clear that no one expects everyone to walk out of here in Almaty with a done deal. This is a negotiating process," said her spokesman Michael Mann.
Iran denies it is developing nuclear weapons and wants the world to respect its "right" to enrich uranium - something current UN sanctions say it cannot do because of its refusal to cooperate with nuclear inspectors.
The Iranians, headed by top nuclear negotiator Saeed Jalili, went into the talks by issuing a string of comments suggesting they were willing to listen to offers without softening their own position.
"We will not accept anything beyond our obligations and will not accept anything less than our rights," Mr Jalili declared before setting off for Kazakhstan.