"I don't think it will take us the same amount of time as it took the Biden administration to come," Khatibzadeh said, referring to US diplomats under President Joe Biden indirectly joining the Vienna talks.

For the government of Iran's ultraconservative new President Ebrahim Raisi, "I don't think the (return to talks) will take as much as 90 days," he said, suggesting talks will be underway again by early November.

It is the first time Iran has suggested a rough date for a possible return to the table.

The 2015 nuclear deal gave Iran sanctions relief in return for tight controls on its nuclear programme, monitored by the UN.

In 2018 then-US president Donald Trump withdrew from the multilateral deal and began reimposing sanctions.

Tehran has gradually rolled back its nuclear commitments since 2019.

Talks in Vienna to revive the deal have been stalled since June, when Raisi was elected as Iran's president. He took office on August 3 and formed his government over the following weeks.

The talks had made little concrete progress and the process then went into a standstill, with Iran saying it needed time after the transition from the more moderate government of Hassan Rouhani.

Khatibzadeh on Monday said Iran's new administration was "examining the details" of the previous rounds of nuclear talks.

"As soon as this is done we will not waste one hour and we will give a new date" for the resumption of discussions, he added.

"The truth is that the executive team tasked with the nuclear (issue) has changed. The (new) negotiators will certainly have different opinions... and they will be presented" when the talks resume, he said.

The foreign ministry spokesman added that the other parties to the talks must embrace the change in Iran's government by showing "flexibility and comprehension".

Biden -- who took office in January -- has signalled a willingness to return to the deal and talks to that end began in April in Vienna, before they stalled.

The talks involve Iran and the remaining parties to the deal -- Britain, China, France, Germany and Russia -- but the US has not participated directly.