Indirect talks between Tehran and Washington on reviving the 2015 Iran nuclear deal have come closer to an agreement, but essential issues remain to be negotiated, the top Iranian negotiator said on Thursday.
Iran and six world powers have been negotiating in Vienna since April to work out steps for both sides to take.
The US in 2018 withdrew from the pact, under which Iran accepted curbs on its nuclear programme in exchange for a lifting of many foreign sanctions against it.
"We achieved good, tangible progress on the different issues," Iranian deputy foreign minister Abbas Araghchi was quoted as saying.
"We are closer than ever to an agreement but there are still essential issues under negotiations."
Mr Araghchi said Iran's presidential election on Friday would have no effect on the negotiations and the Iranian team would continue the talks regardless of domestic policy.
The sixth round of talks resumed on Saturday with the other parties to the deal – Iran, Russia, China, France, Britain, Germany and the EU – meeting in the basement of a luxury hotel.
The US delegation to the talks is based in a hotel across the street because Iran refuses to meet face to face.
Since former US president Donald Trump pulled out of the deal and reimposed sanctions on Iran, Tehran has responded by action against the deal, such rebuilding stocks of enriched uranium.
"We want to make sure that what happened when Trump pulled out of the deal will not be repeated by any other American president in the future," Mr Araghchi said.
Russia's envoy to the talks, Mikhail Ulyanov, said progress had been made in the past few days but talks were tough.
"Some difficult and time-consuming topics still remain unresolved," Mr Ulyanov said.
France's Foreign Ministry said on Wednesday there were still significant disagreements.
Iran's new president is expected to name his Cabinet by mid-August. Current President Hassan Rouhani's term ends on August 3.