The EU top envoy to Iran nuclear talks said on Wednesday he was "quite sure" an agreement would be reached as the negotiations adjourned for a week, Reuters reported.
The talks resumed in Vienna on May 7 among Iran, Russia, China, France, Britain and Germany - meeting in the basement of a luxury hotel, and the United States based in another hotel across the street.
Iran has refused to hold direct talks with the United States on how to resume compliance with the deal, which former President Donald Trump abandoned in 2018.
"I am quite sure that there will be a final agreement... I think we are on the right track and we will get an agreement," Enrique Mora, who is coordinating indirect talks between Iran and the United States, told reporters at the end of a fourth round of negotiations in Vienna.
Russia's envoy, Mikhail Ulyanov, also said on Twitter that participants believed there had been good progress after the latest round of talks and that a deal was "within reach".
Asked if he was saying there would be a deal in the next round, Mora said: "I cannot venture such a prediction. What I can venture is that there will be an agreement, yeah, sure."