Iran has begun enriching uranium to 60 percent — dangerously close to weapons-grade — at an “aboveground facility” at its Natanz nuclear enrichment plant, the U.N. nuclear watchdog said on Saturday, confirming an earlier statement made by Iranian President Hassan Rouhani who said the move came as a direct response to Israel’s “nuclear terrorism” at the plant days earlier.

“The Agency today verified that Iran had begun the production of UF6 enriched up to 60% U-235 by feeding UF6 enriched up to 5% U-235 simultaneously into two cascades of IR-4 centrifuges and IR-6 centrifuges at the Natanz Pilot Fuel Enrichment Plant,” the International Atomic Energy Agency said in a statement to the Reuters news agency.

Sixty percent enrichment leaves a short technical step for centrifuges to obtain weapons-grade 90 percent enrichment or higher. Iran had previously produced 20 percent enrichment, which already violated the terms of the 2015 nuclear deal. The Obama-led agreement, which the Biden Administration is hoping to rejoin, allows for enriched uranium up to 3.67 percent.

“According to Iran’s declaration to the Agency, the enrichment level of the UF6 produced at PFEP was 55.3% U-235. The Agency took a sample of the produced UF6 for destructive analysis to independently verify the enrichment level declared by Iran. The results of this analysis will be reported by the Agency in due course,” an internal, confidential IAEA report obtained by Reuters said.

An April 11 blast at the Natanz facility saw the power supply cut and thousands of centrifuges destroyed, reportedly setting back the country’s nuclear program by nine months.

Iran blamed Israel for the attack. He addressed Israel in televised remarks, saying, “this is the response to your malice. What you did was nuclear terrorism. What we do is legal.”

Rouhani said the first-generation IR-1 centrifuges at Natanz, which were destroyed in the cyberattack, would be replaced by advanced IR-6 centrifuges that can enrich uranium at much greater speeds.

“You wanted to make our hands empty during the talks but our hands are full,” Rouhani said. “We cut both of your hands, one with IR-6 centrifuges and another one with 60%.”

According to former Israeli prime minister Ehud Olmert, who said he had no knowledge of the Natanz attack, the bomb was likely placed there more than a decade ago, waiting for the right time to be detonated.

Over the weekend, Iran state-run television identified Reza Karimi as a suspect in last week’s attack, adding he had since fled the country.