Negotiations in Vienna to revive the 2015 Iran nuclear deal are running out of time and entering their most pivotal stage, European officials said on Monday.
EU foreign affairs chief Josep Borrell said he was optimistic and that the window of opportunity would remain open until the end of this month.
Germany’s Foreign Minister Heiko Maas said the talks, which began in April, have been tough but constructive and much work was still needed.
Iran is discussing its potential return to compliance directly with the deal's remaining signatories – the EU, Germany, France, the UK, China and Russia – while US officials are involved at a separate location in the Austrian capital.
Tehran has repeatedly breached the terms of the accord since former US president Donald Trump withdrew in 2018 and reimposed sanctions on Iran.
“I dare to say that I am optimistic. But a lot of work is needed, time is limited and I hope that the negotiations will enter in a phase of nonstop talks in Vienna," Mr Borrell said as EU foreign ministers met in Brussels.
Asked if a possible agreement in Vienna could provide a platform to addressing the other Iran-related issues, such as its ballistic missile programmes, Mr Borrell was more reserved.
“Lets go step by step. I said that ‘I dare to say that I am optimistic,’ but not about the whole universe. I am optimistic about what’s going on in Vienna.
"This is a very sensitive process. We have to work quickly, we only have a couple of weeks. Not everything will be solved in these couple of weeks, there will be a lot of other issues that will be put on the table later. But for the time being, let's try to go back on track," he said.
The EU, Germany, France, the UK, China and Russia are seeking to return Iran and the US to compliance.
"The negotiations are tough and laborious but all participants are conducting the talks in a constructive atmosphere," Mr Maas said. "However, time is running out. We aim for the full restoration of the Iran nuclear deal as this is the only way to guarantee that Iran will not be able to come into possession of nuclear weapons.”
US President Joe Biden wants his country to return to the deal, but only when Iran stops breaching its terms. Tehran says it will do so when the sanctions are lifted.
The Iran nuclear deal is just one of many talking points on the EU foreign affairs leaders’ agenda in the Belgian capital, with US climate envoy John Kerry due to address the meeting.
On arrival on Monday, Mr Borrell said that after the meeting of G7 ministers in London last week, “it is clear that we have a much better relationship with the US.”
Mr Biden’s administration is seeking to improve US ties with the EU, which deteriorated during Mr Trump’s presidency.