Borrell said a mission this week by EU envoy Enrique Mora to revive the 2015 nuclear pact between Iran and world powers went “better than expected”.
“Negotiations had stalled and have now been resumed,” Borrell said on the sidelines of a G7 meeting in Germany.
“There is a prospect of reaching a final agreement.”
Mora held two-day meetings with Iran’s chief negotiator, Ali Bagheri, in Tehran this week.
Qatar’s Emir, Sheikh Tamim bin Hamad Al-Thani, meanwhile, met with Iran’s Supreme Leader Ayatollah Ali Khamenei and President Ebrahim Raisi on Thursday to urge progress.
The 2015 deal gave Iran sanctions relief in exchange for curbs on its nuclear program to ensure it couldn’t develop nuclear weapons, something Tehran has always denied.
Formally known as the Joint Comprehensive Plan of Action, the life-support agreement was abandoned in 2018 by then-US President Donald Trump’s unilateral decision to withdraw and impose punitive sanctions.
This prompted Iran to scale back its own commitments.
Trump’s departure from office has restarted efforts to revive the deal, with Mora playing a key role during a year of on-off talks in Vienna.
One of the key sticking points in the negotiations was Tehran’s demand that the US remove Iran’s Islamic Revolutionary Guard Corps from a designated list of terrorist groups.
Borrell said “these disagreements over what to do with the Revolutionary Guards” had hampered the talks’ progress for two months.
He said Mora brought the EU’s message to Tehran “that we cannot go on like this”.
“The response was positive enough,” Borrell said.
“Things like that can’t be solved overnight. Let’s say things got blocked and they got unblocked.”
Borrell declined to comment on Mora’s tweet that he was briefly detained by German police at Frankfurt Airport, saying only that “the matter is settled.”
Mora had tweeted earlier on Friday that he had been “detained by German police” on the journey back to Brussels.
“Not a single explanation. An EU official on official mission with a Spanish diplomatic passport,” he wrote.
After his release, he tweeted that he had still not received “an explanation for an apparent violation of the Vienna Convention.”
Initially, there was no comment from the German police.
