Iran's President Hassan Rouhani said Wednesday a breakthrough in talks in Vienna to revive a nuclear deal before he leaves office in August required a "will" beyond his power.

Rouhani is Iran's main architect of the 2015 nuclear agreement with world powers, which was torpedoed by former US president Donald Trump in 2018.

Under its terms, international sanctions against Iran were eased in return for a commitment from Tehran that it would not seek to develop nuclear weapons.

But the final decision regarding the ongoing Vienna negotiations rests with the Islamic republic's supreme leader Ayatollah Ali Khamenei.

"Our main issues with the United States in these negotiations have been resolved, and there are only a few minor issues left, on which we will negotiate and produce results," Rouhani said, at a televised cabinet meeting.

"If there is the will that this be done in the current administration, then this administration has finished the work," he added.

Iranians vote on June 18 for a new president, Rouhani having served the maximum two consecutive terms allowed under the constitution. He will hand over power in August.

Negotiations have been underway since April in the Austrian capital between Iran and the remaining members to the accord, Britain, China, France, Germany and Russia.

Talks resume next week

Mikhail Ulyanov, the Russian envoy at the talks, tweeted they had reached a point where the different countries needed to consult with their respective capitals.

The talks have been halted on Wednesday but are due to resume at the end of next week, he added.

EU negotiator Enrique Mora, who is chairing the talks in Vienna, told journalists Wednesday he hoped that it would be the last round of negotiations.

"But we are going to keep working and I am sure that at the next round next week we will finally have an agreement," he added.

In Washington, US State Department spokeswoman Jalina Porter spoke of progress, while cautioning that reaching an agreement would be neither a fast nor an easy process.

The United States is participating indirectly in the talks.

Trump's successor, US President Joe Biden, has signalled his readiness to revive the nuclear deal.

For this to happen, the US would need to return to the accord and lift the sanctions reinstated by Trump, while Tehran would have to re-commit to full compliance with nuclear obligations it progressively withdrew from since 2019 in retaliation.

Sanctions reimposed by Trump deprived Iran of the economic benefits the deal had promised, especially by blocking its vital oil export lifeline and access to its funds abroad, sparking an economic crisis.