Iran’s top diplomat said on Tuesday that an attack on its Natanz nuclear facility which it blames on Israel was a “very bad gamble” that would strengthen Tehran’s hand in talks to revive a 2015 nuclear deal with major powers.

Tehran has said an explosion on Sunday at its key nuclear site was an act of sabotage by arch-foe Israel and vowed revenge for an attack that appeared to be latest episode in a long-running covert war. Israel, which the Islamic Republic does not recognise, has not formally commented on the incident.

“Israel played a very bad gamble if it thought that the attack will weaken Iran’s hand in the nuclear talks,” Iranian Foreign Minister Mohammad Javad Zarif told a joint news conference with his Russian counterpart in Tehran.

“On the contrary, it will strengthen our position.”

Iran and the global powers held what they described as constructive talks last week to salvage the 2015 nuclear accord, which Israel fiercely opposed.

Former US President Donald Trump abandoned the deal, which lifted economic sanctions on Iran in return for curbs to its nuclear program. He reimposed US sanctions, prompting Iran in turn to violate the accord’s atomic limits.

US President Joe Biden has said Tehran must resume full compliance with restrictions on its nuclear activity under the deal before Washington can rejoin the pact.

Iran and remaining parties to the deal will resume talks in Vienna on Wednesday.

Washington has suggested that it might be willing to ease some sanctions on Iran beyond those whose removal was mandated by the original nuclear deal. But Iran insists that all sanctions should be lifted at once.

“The United States should know that neither sanctions nor sabotage will give them the means to negotiate, and that they will only make the situation more difficult for them,” Zarif said.

The White House said on Monday the United States was not involved in Sunday’s attack and had no comment on speculation about the cause of the incident.

“Sunday’s sabotage occurred in a power cable duct leading to the centrifuge machines. This was not an external attack and the location of the sabotage has been clearly determined,” Iranian government spokesman Ali Rabiei was quoted by state media as saying.

Rabiei appeared to be referring to a person the Iranian authorities have said caused the electricity outage at Natanz and whose arrest is being sought. Rabiei said the damage caused could be quickly repaired.

Iranian authorities say uranium enrichment has not stopped at the site.

“What happened in Natanz makes it possible for Iran to legally do whatever it takes to ... compensate for this terrorist stupidity,” said Zarif. “I assure you that in near future, the Natanz site will move forward with more advanced centrifuges.”