Enrique Mora spoke a day after ultraconservative cleric Ebrahim Raisi won the Islamic republic's presidential election.

Sunday's meeting was part of regular discussions since early April, aimed at bringing the US back to the 2015 landmark agreement and Iran back into compliance with curbs on its nuclear programme in exchange for sanctions relief.

But it came a day after Raisi was declared the winner of Iran's presidential election, replacing moderate Hassan Rouhani.

"We are closer to a deal, but we are not still there," EU negotiator Mora, who is chairing the talks, told reporters.

Mora added that he expected in the next round "the delegations will come back from the capitals with clearer instructions, clearer ideas on how to finally close the deal."

He did not say when talks would resume, noting that the main problem continued to be to find a solution "in this delicate balance" between lifting US sanctions on Iran and reversing Tehran's stepped-up nuclear activities.

Mora said the next round would also give "a clearer idea" of Iran's "new political environment" though he pointed out that talks had carried on despite the election.

Iran's envoy, Deputy Foreign Minister Abbas Araghchi, said ahead of Sunday's meeting that negotiators were "closer to an agreement than ever.

"But it is not an easy task to close the distance currently between us and an agreement," he told Iran's national television.

"At this point, it is clear which fields, which actions are possible and which are not. Therefore, it is time for all sides, especially our counterparts, to be able to make their final decision."

Araghchi could not say how many days the latest break would last.

Parties to the agreement -- Britain, China, Germany, France, Russia and Iran -- have been meeting in Vienna with indirect US participation to restore the deal, which promised Tehran sanctions relief in exchange for curtailing its nuclear programme.

They had hoped to finish the talks before the Iranian presidential election, but it had become clear recently that they would miss that target.

The deal was thrown into disarray in 2018 when then US president Donald Trump withdrew and reimposed sanctions, leading Iran in turn to step up its nuclear activities from 2019 onwards.

In February, Tehran also suspended some inspections by the UN nuclear watchdog, forcing the International Atomic Energy Agency (IAEA) to negotiate continued though reduced access.

The latest understanding runs out on June 24.

"We continue to follow the issue. Iran is talking to the agency and to director general Rafael Grossi so we expect that they will reach an agreement and we can continue our negotiations in a good framework," Mora said.

burs-jza/wai