Iran's chief nuclear negotiator, Abbas Araqchi, said earlier on Twitter that the next round of negotiations in Vienna must wait until the new Iranian administration takes office in August but insisted that a prisoner exchange could take place quickly if the United States and Britain would stop linking it with the nuclear issue.

Indirect US-Iranian talks on reviving the 2015 deal have been on hold since the last round ended on June 20, and Araqchi's comments confirmed that Tehran will not return to the table before President-elect Ebrahim Raisi takes over.

"We're in a transition period as a democratic transfer of power is under way in our capital. Vienna talks must thus obviously await our new administration,” he tweeted.

For his part, US State Department spokesman Ned Price said: "These comments are an outrageous effort to deflect blame for the current impasse."

"We stand ready to return to Vienna to complete work on a mutual return to the JCPOA once Iran has made the necessary decisions,” Price said, referring to diplomatic efforts to get both countries back to the Joint Comprehensive Plan of Action, according to Reuters.

That is the nuclear accord that former President Donald Trump abandoned and his successor, President Joe Biden, seeks to revive.

Araqchi also urged the United States and Britain to stop linking any exchange of prisoners with the nuclear deal. "Ten prisoners on all sides may be released tomorrow if US&UK fulfil their part of a deal," he said.

In response, Price said: “With respect to the comments on the Americans whom Iran has unjustly held against their will, we see just another cruel effort to raise the hopes of their families … There is no agreed deal yet."

“We had been engaged in indirect talks on the detainees in the context of the Vienna process, and the delay in restarting that process is not helping,” Price added. “While it would be more effective to make progress if we were meeting in Vienna, we are also prepared to continue with talks on detainees during this period.”

Iran, which is holding a handful of Iranian-Americans, has been accused by rights activists of arresting dual nationals to try to extract a concession from other countries. Iran has dismissed the charge.

Iran said earlier this week that it was holding talks on securing the release of Iranian prisoners in American jails and other countries over violations of US sanctions.

In May, Washington denied a report by Iranian state television that the countries had reached a prisoner swap deal in exchange for the release of $7 billion in frozen Iranian oil funds under US sanctions in other countries.

The hiatus in nuclear talks, which US and European officials attribute to hard-line Raisi's election, has raised questions about next steps if the talks hit a dead end.