Nuclear talks with Iran are close to reaching a deal, the chief British envoy said on Friday as she and her French and German colleagues flew home to brief ministers.

"We are close. E3 negotiators leaving Vienna briefly to update Ministers on state of play. Ready to return soon," Stephanie Al-Qaq said on Twitter, referring to the chief British, French and German diplomats involved in the talks.

Despite the British diplomat's teasing Twitter post, two sources with direct knowledge said there was still no deal and European and Iranian officials said that Iran's lead negotiator, nuclear negotiator, Ali Bagheri Kani was staying in Vienna.

Negotiators have worked for 11 months to try to revive the 2015 deal, known as JCPOA, under which Iran limited its nuclear program to make it harder to obtain fissile material for a bomb - an ambition Tehran denies - in return for relief from economic sanctions.

Then-US President Donald Trump reneged on the pact in 2018, restoring US sanctions that have slashed Iran's oil exports. Iran followed suit by increasing the level of its uranium enrichment violating the deal's nuclear limitations.

It is not clear what exactly the remaining issues are in the talks, but the head of the International Atomic Energy Agency is flying to Iran on Saturday to iron out past issues of suspected clandestine nuclear activities.

With reporting by Reuters