An alleged act of sabotage against a key Iranian nuclear site appears to have complicated newly launched negotiations aimed at reviving the 2015 nuclear deal.
Two days after the attack -- which Iran has blamed on Israel -- Tehran announced it will start enriching uranium at 60 percent purity, higher than it has ever done before.
Iranian President Hassan Rohani said on April 14 that the decision to sharply boost the enrichment was a reaction to the alleged attack at the secretive underground facility in central Iran.
"Enabling IR-6 [centrifuges] at Natanz today, or bringing enrichment to 60 percent, this is the response to your evilness," Rohani, apparently alluding to Israel, said at a cabinet meeting. "What you did was nuclear terrorism. What we do is legal."
Iranian authorities have called the damaging attack on Natanz an act of "nuclear terrorism," suggesting it was aimed at undermining recently launched, indirect negotiations between Tehran and Washington held to try to find a way for the United States to rejoin the deal it left in 2018 in exchange for Iran strictly adhering to the agreement.
"You wanted to leave our hands empty during the talks but our hands are full," Rohani said, suggesting that Tehran was attempting to gain leverage in the talks in Vienna, which are due to resume later this week.
Tehran's decision to enrich uranium at unprecedented levels was announced two days after the April 11 incident at Natanz. Iran's envoy to the International Atomic Energy Agency (IAEA), Kazem Gharibabadi, said on April 14 that 60 percent enrichment would begin next week.
Under the nuclear deal agreed between six world powers and Iran, Tehran is allowed to enrich uranium at 3.67 percent. Nuclear enrichment of 90 percent purity is needed to produce a nuclear bomb.
Tehran began enriching uranium to 20 percent in January after parliament passed a law requiring the government to boost enrichment levels. The bill was adopted following the November 2020 assassination of top Iranian nuclear scientist Mohsen Fakhrizadeh amid suspicions that Israel was behind the killing near Tehran.
Analysts have warned that the incident at Natanz -- which involved a carefully timed disruption of the site's power -- was likely to make it more difficult for Iranian negotiators to compromise in the nuclear talks, at which European countries have worked as intermediaries between Tehran and Washington.
"Domestic politics in Iran were already making compromise hard, this is just going to pour gasoline on that problem," Eric Brewer, a senior fellow at the Center for Strategic and International Studies, told RFE/RL.
"Enriching to 60 percent is a significant Iranian step and will further shorten Iran's breakout timeline," said Brewer, who served as a deputy national intelligence officer and was responsible for monitoring Iran's nuclear program.
He added that the move was "unlikely to have the intended effect of forcing the U.S. to accept Iran's demands."
Iranian Foreign Minister Mohammad Javad Zarif said sabotaging Natanz was "a very bad gamble" that he claimed would strengthen Tehran's hand in the nuclear talks.
He also said Tehran will retaliate if it determines that Israel was behind the sabotage. "The Zionists want to take revenge for our progress on the way to lift cruel sanctions," Zarif said earlier in the week, adding that "we will not fall into their trap."
The extent of the damage to the underground nuclear site is not clear. Citing two intelligence sources, The New York Times reported that production at Natanz could be set back for at least nine months due to the attack, which reportedly caused fires.
Lawmaker Alireza Zakani, who heads the research center of Iran's hard-line parliament, said in an interview that "several thousand centrifuges were damaged and destroyed."
Israel has neither denied nor confirmed a role in the incident. Unnamed intelligence sources have told Israeli media that Mossad was responsible for the sabotage.
The White House has denied that the United States had any involvement in the incident while declining to comment on whether the incident might undermine efforts to restore the nuclear accord.
'Not A Small Signal'
Brewer said the attack at Natanz signalled to Iran that "its adversaries can still 'reach out and touch' its nuclear program whenever they feel like it."
"After years of attacks against Iranian facilities and scientists and efforts Iran has taken to prevent them, [that attack is] not a small signal," he said, adding that more events, "deliberate and otherwise," are expected that could test the talks.
"For diplomacy to work we have to weather those events, and we've done so before. But that's a lot harder right now given that we're probably a ways off from a deal and there's a lack of trust," he added.
Ali Vaez, director of the Iran project at the International Crisis Group, said the attack at Natanz appeared to be "a win-win scenario for Israel."
"If Iran doesn't retaliate out of fear of derailing nuclear diplomacy, it grants Israel a cost-free but devastating blow to Iran's nuclear program. If Iran retaliates, then it risks derailing nuclear diplomacy, which is in line with Israel's objectives," he told RFE/RL.
Dalia Kassa Kaye, a fellow at the Wilson Center and the former director of the Rand Center for the Middle East, believes undermining diplomacy was not the only aim of the attack at Natanz, which was also targeted in July in an act of sabotage that was also blamed on Israel as part of shadow efforts undermining Iran's nuclear program, which Israeli officials see as an existential threat.
"But such incidents certainly complicate diplomacy for the [administration of President Joe Biden] and are only likely to further erode trust between the United States and Iran," she said. "It's hard to imagine the administration welcomed this action in the midst of this particularly sensitive time in nuclear diplomacy."
The incident resulted in a call by Iran's Tasnim news agency, which is affiliated with the powerful Islamic Revolutionary Guards Corps, for Rohani's government to leave the Vienna talks that the news outlet said were taking place "under the shadow of terror." Tasnim suggested the Natanz attack must have been coordinated with the United States.
Lawmaker Mojtaba Zolnur, who heads parliament's National Security and Foreign Policy Committee, called on Rohani not to trust Washington, saying Israel's "involvement" in the incident did not clear the United States, which he claimed had been working "to inflict more severe blows" on Tehran.
But Reza Noroozpur, the head of the official IRNA state news agency, warned against halting the negotiations, saying it was "the demand of [Israeli Prime Minister Benjamin] Netanyahu." He added that Tehran should follow the policy of "strategic patience" and retaliate at an appropriate time.
U.S. President Donald Trump exited the landmark agreement in May 2018 while reimposing crippling economic sanctions at the same time. Tehran reacted by gradually decreasing its commitments under the deal.
The Biden administration has expressed its readiness to rejoin the nuclear deal -- also co-signed by Germany, France, Russia, Britain, and China -- if Tehran returns to full compliance with the agreement.
Washington said last week it would be prepared to lift sanctions that are inconsistent with the nuclear agreement.
But Tehran has called for the removal of all sanctions in refusing any direct talks with Washington, saying that it is no longer a party to the agreement.