Diplomatic efforts to engage Iran will continue after an apparent attack on Tehran's nuclear site at Natanz, the US defence secretary said as he left Israel on Monday.
Lloyd Austin said he was aware of reports of the attack, which Iran blamed on Israel, but had no details.
Iran said on Sunday that it's underground Natanz site had been sabotaged after it experienced power cuts. Foreign Minister Javid Zarif accused Israel of carrying out "nuclear terrorism".
“I’m aware of the reports. I really don’t have anything to add on Natanz," Mr Austin said from Israel's Navatim airbase.
"In terms of, you know, our efforts to engage Iran in diplomacy on the JCPOA, those efforts will continue. And I’m very obviously supportive of the president’s efforts to negotiate a way ahead there. And I’ll just leave it at that.”
Mr Austin reiterated US support for Israel's security in remarks made alongside Prime Minister Benjamin Netanyahu after a meeting on Monday.
Mr Netanyahu said the US and Israel agreed that "Iran must never possess nuclear weapons".
“In the Middle East there is no threat that is more serious, more dangerous, more pressing, than that posed by the fanatical regime in Iran.”
“Iran continues to support terrorists around the world in five continents, threatening civilians everywhere.”
“Iran has never given up its quest for nuclear weapons and the missiles to deliver them, and Iran consistently and outrageously calls for Israel’s annihilation and works towards that goal.”
“My policy as prime minister of Israel is clear. I will never allow Iran to obtain the nuclear capability to carry out its genocidal goal of eliminating Israel. And Israel will continue to defend itself against Iran’s aggression and terrorism.”
Mr Austin' two-day visit to Israel included talks on security co-operation with Israeli Defence Minister Benny Gantz and a tour of Israeli air and missile defence systems and its fleet of F-35 combat aircraft.
Mr Gantz gave Mr Austin a model of the David’s Sling missile system and Mr Austin presented Mr Gantz with the original communique in which the US officially recognised the establishment of the state of Israel.
Natanz sabotage allegations
Details remain scarce about what happened early on Sunday at Natanz.
The event was initially described as a power failure of the electrical grid feeding its above-ground workshops and underground uranium enrichment halls.
While there was no immediate claim of responsibility, suspicion fell immediately on Israel, where several news outlets reported a devastating cyberattack on the Iranian site, orchestrated by the country's intelligence services.
Mr Austin arrived in Israel just as Iran reported that the site lost power hours after starting up new advanced centrifuges capable of enriching uranium faster.
If Israel caused the blackout, it would further heighten tensions between the two nations, already engaged in a shadowy conflict across the wider Middle East.
Mr Austin's visit to the region comes as his colleagues in the Biden administration meet in Vienna with Iranian counterparts, as part of President Biden's attempt to work out an arrangement to re-enter the Iran nuclear deal.
Israel's government has for years described Iran as an existential threat due to its alleged pursuit of a nuclear weapon and its support for militant groups like Lebanon’s Hezbollah.