A mysterious explosion that caused a blackout at Iran’s nuclear enrichment facility last weekend prompted suggestions from the Islamic Republic that its old foe Israel was responsible.

Israel is usually tight-lipped after an unexplained attack, whether the November assassination of a leading Iranian nuclear scientist, cyber attacks designed to slow Tehran’s enrichment ability or assaults on Iran-linked ships travelling in international waters.

This time, however, in officially sanctioned leaks to local media and the US press, Israel all but claimed credit for last weekend’s attack.

Its public embrace of a shadow conflict with Tehran is aimed at complicating the US-brokered talks over Iran’s nuclear programme that have been given new life by Joe Biden’s presidency, according to Israeli, European and US officials and analysts who spoke to the Financial Times.

“Israel wants to make the position [over nuclear talks] harder for the American administration and send the message to the Iranians that we’re stronger and we don’t need to hide when we’re doing something,” said Eldad Shavit, an Israeli army reserves colonel and former intelligence officer.

For Benjamin Netanyahu, Israel’s veteran prime minister, the escalation is part of a decade-long rejection of the idea that Iran’s ambitions can be tamed by diplomacy.

His position, say people familiar with his thinking, is both politically expedient — Iran is a potent symbol in Israeli politics — and driven by a deeper fear of the existential threat posed by Tehran. In his assessment, Israel’s own undeclared covert nuclear weapons programme — active since the 1970s and operational since the 1980s — is not a sufficient deterrent.

Netanyahu sacrificed his relationship with President Barack Obama by aggressively courting Republicans opposed to the nuclear accord signed with world powers in 2015. While Netanyahu was vindicated when Donald Trump ripped up the deal in 2018 and imposed crushing sanctions on Iran, the Israeli leader now fears a return to Obama-era rapprochement.

Netanyahu has in the past few years authorised hundreds of air strikes on Iranian-linked targets in Syria, and more recently stepped up covert actions. An assessment from the US intelligence community this week described a pattern of “iterative violence between Israel and Iran”.

“If you put together all the things Israel’s doing, what they’re saying . . . is that going back to [the nuclear deal] isn’t going to stop us, we don’t believe in it and you’re going to have to go further,” said Elliott Abrams, the Trump administration’s former Iran envoy. Israel believes that without “additional limits on the Iranian nuclear programme or on Iranian support for terrorist groups we will have to act in our own self defence”, he added.

Israel has always said the Iran deal is insufficiently broad because it does not include curbs on Iran’s pursuit of ballistic missiles and its regional ambitions, including backing Shia militia groups in Iraq, Lebanon and Syria.

Netanyahu has also alleged that Iran always intended to renege on the deal, trumpeting a secret nuclear archive that Mossad agents spirited out of a warehouse in Tehran.

“Israel has had a long-running war with Iran, even if it has been a secret war with a low-profile,” said Sima Shine, a former Mossad official and head of the Iran programme at the Institute for National Security Studies. “Now, there’s an interest in Israel to deter Iran, and to make them think we can penetrate any place every time they jeopardise our national security.”

Iran responded to the blackout by this week stepping up its uranium enrichment to 60 per cent, its highest ever level. Weapons-grade uranium is enriched to 90 per cent.

“These are our responses to your viciousness,” Iran’s president Hassan Rouhani said on Wednesday, even as nuclear talks with world powers were restarting in Vienna. “You wanted to make our hands empty during the talks but our hands are full.”

Iranian officials agree in private that Netanyahu’s intention is to derail the talks, while covert actions delay the nuclear programme.

“Israel has a record of destroying Iraqi and Syrian nuclear programmes and has the self-defined mission to do the same with Iran’s but not through bombardment rather sabotage,” said an Iranian hardliner. “It’s sending a message to the Americans that they don’t need to contain Iran through the talks and hence no need to lift the sanctions.”

A US National Security Council official said Washington and Tehran had a “common objective” of returning to the nuclear accord. The Vienna talks were the best way to limit Iran’s nuclear ambitions and to “address the full range of concerns that we have with Iran’s activities in the region and beyond”, the person added.

Mike Eisenstadt, a former US government military analyst now with the Washington Institute think-tank, argued Israel’s covert actions could give the Biden team leverage. “It kind of puts daylight between the US and Israel and buys time for negotiations,” he said.

European diplomats have expressed dismay at the tit-for-tat conflict and its capacity to damage the Vienna talks.

One described it as a “vicious circle” and said Iranian retaliation through moving to 60 per cent enrichment “could seriously complicate things” in the Austrian capital. Another European official said there was “one actor who is not interested in the talks” and was attempting to “undermine the diplomatic efforts” — a clear reference to Israel.

But the official also expressed hopes that other parties wanted the nuclear deal “back on track”, including Iranian hardliners who need sanctions lifted to bring economic benefits and ease domestic political pressures.

“In the end it will be about what kind of compromise will be found . . . and which they can sell as their win and show they were not the ones who have backed down,” the official said.