German Foreign Minister Annalena Baerbock attends day one of the G7 summit of foreign and development ministers at the Museum of Liverpool, in Liverpool, Britain, December 11, 2021. (Photo: REUTERS)

Talks have resumed in Vienna to try to revive the nuclear pact, with both sides trying to gauge the prospects of success after the latest exchanges in the stop-start negotiations.

German Foreign Minister Annalena Baerbock said Iran had resumed the talks with a position that set the negotiations back six months. The current round of talks in Vienna follow a pause of five months after the election of Iran's president Ebrahim Raisi.

Earlier, US officials said Secretary of State Antony Blinken had held a "productive" meeting with his counterparts from Britain, Germany and France on Friday, discussing the way forward for the Iran talks.

A senior State Department official said there was an "intense" conversation among the G7 countries, which were united in their position on the nuclear talks. The official added that US Special Envoy for Iran Robert Malley was heading back to Vienna for talks.

Iranian officials have previously said they were sticking to their tough stance.

Under the original nuclear deal, abandoned in 2018 by then-President Donald Trump, Iran limited its nuclear programme in return for relief from US, European Union and UN sanctions.

Iran's president Ebrahim Raisi said on Saturday that Tehran was serious in its nuclear talks in Vienna.