The European Union has said it is studying Iran's response to a "final" draft agreement on reviving a 2015 nuclear accord with major powers it presented at talks in Vienna.
The United States had already said on Monday that it was informing EU foreign policy chief Josep Borrell of its response to the text he submitted on August 8.
A spokesperson for Borrell — who coordinated talks to bring Iran and the US back into the deal — said on Tuesday that the Iranian response was received late on Monday and the EU was consulting with the US and the other parties "on the way ahead".
"Everybody is studying the response and this is not the time for the moment to speculate on timing," Borrell's spokesperson Nabila Massrali later told a press briefing.
Earlier on Tuesday, Iran's official IRNA news agency reported that "an agreement will be concluded if the US reacts with realism and flexibility" to Iran's response.
Iran's ISNA news agency cited an "informed source" as saying that Tehran "expects to receive the response of the other side in the next two days".
The possibility of a deal which might lead to the lifting of US sanctions on Iran's oil output of 2.5 million barrels per day has already helped trigger a fall in prices on world markets, with US oil futures dropping nearly three percent to finish below $90 a barrel.
IRNA had said on Friday that Iran might accept the "final" text drawn up by the EU to save the deal, which aimed to curb Iran's nuclear programme in return for sanctions relief.
The deal has been moribund since the 2018 withdrawal of the US under then-President Donald Trump whose administration reimposed crippling sanctions.
IRNA said that the remaining differences centred on three issues.
"The US has expressed flexibility on two of them verbally but that needs to be incorporated into the text," the news agency said without elaborating.
"The third issue has to do with a guarantee that the deal will be lasting, and that depends on realism from the US to reassure Iran."
None of the parties have spelt out in details the points of contention that are still blocking a deal.
Iran's demand for an end to US blacklisting of the Revolutionary Guards as a terrorist organisation has been dropped from the discussions and will instead be handled after the deal, a senior EU official said earlier this month.
The official said progress had also been made on Tehran's call for guarantees that there will be no repeat of Washington reneging on the deal as it did under Trump in 2018.
Tehran and Washington still have to agree on "issues related to sanctions lifting and a couple of nuclear questions that did not exist in March as the Iranians advanced their programme", the EU official said.
Iran also wants the UN nuclear watchdog, the IAEA, to end its long-running investigation into traces of enriched uranium found at sites not declared as having hosted nuclear activities.