"We will resume the talks on the JCPOA in the coming days... I mean quickly, immediately," Borrell told a news conference in the Iranian capital, referring to the Joint Comprehensive Plan of Action.

Borrell made the announcement after a two-hour meeting with Iran's Foreign Minister Hossein Amir-Abdollahian on the second day of a previously unannounced visit to the Islamic republic.

Amir-Abdollahian confirmed the resumption of the negotiations.

"We have had a long but positive conversation on global cooperation between Iran and the EU," Amir-Abdollahian said. "We will try to solve the problems and differences through the negotiations that will resume soon."

The Iran nuclear deal has been hanging by a thread since 2018, when then US president Donald Trump unilaterally withdrew from the accord and began imposing crippling economic sanctions on America's arch enemy.

The administration of incumbent US President Joe Biden has sought to return to the agreement, saying it would be the best path with the Islamic republic.

The talks began in April last year but stalled in March amid differences between Tehran and Washington, notably over a demand by Iran to remove its Islamic Revolutionary Guard Corps from a US terror list.

- 'Meaningful diplomacy' -

On the eve of Borrell's trip, the US pointman on Iran, Robert Malley, had "reiterated firm US commitment to come back to the deal" over a meal with the EU diplomatic chief, according to the EU's coordinator for the talks, Enrique Mora.

"We remain committed to the path of meaningful diplomacy, in consultation with our European partners," Malley said in a tweet.

France, one of the six world powers that agreed the 2015 deal, had on Friday appealed to Iran to "seize this diplomatic opportunity to conclude now, while this is still possible".

Amir-Abdollahian said on Thursday that Iran was "serious" about reaching an agreement while calling for "realism from the American side".

The nuclear deal reached with six major powers -- Britain, China, France, Germany, Russia and the US -- gave Iran relief from sanctions in return for guarantees it could not develop an atomic weapon.

Iran has always denied wanting a nuclear arsenal.

- Cameras removed -

In April, Secretary of State Antony Blinken said the United States still believed a return to the accord was "the best way to address the nuclear challenge posed by Iran".

Blinken warned at the time that the "breakout time" for Iran to develop a nuclear bomb if it so chooses was "down to a matter of weeks" after the deal pushed it beyond a year.

The International Atomic Energy Agency's board of governors adopted a resolution this month censuring Iran for failing to adequately explain the previous discovery of traces of enriched uranium at three sites which Tehran had not declared as having hosted nuclear activities.

On the same day, June 8, Tehran said it had disconnected a number of IAEA cameras that had been monitoring its nuclear sites.

IAEA chief Rafael Grossi later confirmed 27 cameras had been disconnected, leaving about 40 still in place.

The move by Iran, he warned, could deal a "fatal blow" to the negotiations unless the UN nuclear watchdog's inspectors were given access within three to four weeks.

The visit by Borrell, his first to Tehran since February 2020, could be a determining factor in the fate of the deal.

During the talks in Vienna aimed at reviving the accord, Iran has repeatedly called for guarantees from the Biden administration that there will be no repeat of Trump's pullout.