The landmark JCPOA deal has been in tatters since then-president Donald Trump withdrew the United States from it in 2018 and Iran later backed away from some of its own commitments.

On-off talks have been underway since 2021 to revive the deal, which gave Iran much-needed sanctions relief in return for curbs on its nuclear program.

"It's not that we don't want to see the JCPOA reimplemented, we of course do. We're just not in a position where... that's a likely outcome anytime in the near future," White House spokesman John Kirby told reporters.

"What we're focused on is holding the (Iran) regime accountable for what they are doing to these innocent political protesters."

Protests and unrest have gripped the Islamic republic since Mahsa Amini, 22, died on September 16 after being arrested by the morality police in Tehran for allegedly violating the strict dress code for women.

The European Union had submitted in August a final draft of a modified nuclear text for the agreement, but there are key sticking points between Tehran and Washington and the UN nuclear watchdog.

President Joe Biden is "committed to not allowing Iran to achieve a nuclear weapons capability," Kirby said.

"The president still believes that a diplomatic way forward is the best way forward to achieve that outcome.

"At this time, the Iranians have come back with unreasonable demands, many of which have nothing to do with the deal itself."

In contrast, Iranian foreign ministry spokesman Nasser Kanani said earlier this month that the deal could still be revived and that work was ongoing.