Talks in Vienna aimed at reviving the Iran nuclear accord could lead to a deal at the sixth round of negotiations, which begins next week, the EU's envoy to the talks said.
Enrique Mora said after the conclusion of the fifth round of talks that several “rather complex” technical issues remained but that “there are fewer than there were one week ago”.
“I’m sure that the next round will be the one in which we will finally get the deal," he said.
US State Department spokesman Ned Price, however, was more circumspect in his outlook, saying that while the US expected to enter into a sixth round of talks, subsequent rounds were also possible.
"Challenges remain" in reviving the 2015 nuclear accord that former president Donald Trump abandoned in 2018, Mr Price told reporters.
“There's just about every expectation there will be subsequent rounds” of talks, Mr Price said.
He added that he was "neither optimistic nor pessimistic" on the chances of getting a deal.
Following the completion of the fifth round of talks this week, delegations from China, France, Germany, Iran, Russia, Britain and the US will return home to brief their governments.
Mr Trump unilaterally withdrew from the deal in 2018 and reimposed sanctions on Iran. In response, Tehran repeatedly breached the terms of the accord.
The talks in Vienna, which began in early April, seek to bring both sides back into compliance.
Mark Fitzpatrick of the International Institute for Strategic Studies pointed to a number of sticking points that appear unresolved in Vienna.
One issue "is how to restore the one-year break-out time, that is, the time it would take Iran to produce a weapon's worth of highly enriched uranium," the former US diplomat and non-proliferation expert told The National.
"The advanced, highly efficient centrifuges that Iran has introduced will probably have to be destroyed rather than just taken offline, but Iran is resisting doing that."
But Mr Fitzpatrick said the sanctions may be an even greater issue.
"Iran insists that all sanctions imposed under the Trump administration must be removed, even those that were applied for reasons that are extraneous to the [deal] and would not impede its restoration," he said.
"For example, Iran insists that the Islamic Revolutionary Guard Corps come off the US Treasury blacklist, something the US resists because President Biden would be accused of coddling terrorists," Mr Fitzpatrick said.
Mr Mora’s relatively upbeat tone contrasted with that of officials from other European countries that were signatories to the 2015 accord, in which Tehran agreed to limit its nuclear ambitions.
"We have made further progress and important aspects of a future agreement have been worked out," European diplomats said.
"However, the most difficult decisions still lie ahead. Of course, we always work on the basis of 'nothing is agreed until everything is agreed'."
The diplomats said there was an awareness that time was running out and that decisions needed to be made soon.
While Iranian and American diplomats are present in Vienna, they are not directly negotiating with each other.
Iranians vote on June 18 for a new president, with Hassan Rouhani having served the maximum two consecutive terms allowed under the Iranian constitution.
Mr Rouhani, who will leave office in August, also struck a relatively optimistic tone.
"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,” he told a Cabinet meeting.
"If there is the will that this be done in the current administration, then this administration has finished the work."
But Mr Fitzpatrick said Iranian hardliners do not want a deal before the election "for fear that it would detract from the expected victory of their preferred candidate", Iran's chief justice Ebrahim Raisi.
US State Department spokeswoman Jalina Porter said “some progress had been made".
“Talks are ongoing and they will continue at a pace that’s honestly appropriate to address the significance of the issues that are currently on the table and being negotiated right now,” she said.
