In a phone call with US Secretary of State Antony Blinken, Bennett, who has been a consistent opponent of the 2015 agreement the powers have been seeking to revive, called instead for "concrete measures" to be taken against Iran.

He said "Iran was carrying out 'nuclear blackmail' as a negotiation tactic and that this must be met with an immediate cessation of negotiations and by concrete steps taken by the major powers," a statement from his office said.

It said Blinken had updated Bennett on what had been happening in the talks since their resumption on Monday after a five-month hiatus.

The Israeli premier expressed concern about a new report from the UN nuclear watchdog issued during the talks which he said showed Iran had "started the process of enriching uranium to the level of 20% purity with advanced centrifuges at its Fordo underground facility".

A year after then US president Donald Trump pulled out of the nuclear agreement in 2018 and started imposing sweeping sanctions, Iran began a gradual suspension of its undertakings in the deal.

The countermeasures have seen Iran enrich uranium in greater quantities and to higher levels of purity than it had agreed, something Western governments are eager to end as quickly as possible.

Iran insists the absolute priority is the lifting of all US sanctions imposed after Trump's abandonment of the deal.

The remaining parties to the 2015 agreement -- Britain, China, France, Germany and Russia -- have been participating directly in the Vienna talks. At Iran's insistence, the United States is doing so only indirectly.