Iranian Foreign Minister Mohammad Javad Zarif has written to United Nations Secretary-General Antonio Gutteres saying that the Iranian nuclear program will take "a significant upward leap" if the United States does not act to lift sanctions and stop “nuclear terrorism”, that Tehran has blamed on Israel.

In a letter published Tuesday (April 13) on the foreign ministry website, Zarif pointed out that the Natanz facility was under a UN inspections regime and that targeting it carried a “high risk of potential release of radioactive material” and amounted to “reckless criminal nuclear terrorism."

The Iranian foreign minister said Iran was “refraining from any final judgement as to the culprit” while an investigation continued, but pointed out that Israeli officials had since late 2020 publicly threatened to sabotage any attempts to restore Iran’s 2015 nuclear deal with world powers, the Joint Comprehensive Plan of Action (JCPOA).

Zarif suggested that at least indirect US indirect involvement was suspected: "If the United States wants to avert the drastic consequences of foolish gambles by its terrorist stooges, it must cease forthwith to consider unlawful measures—whether economic terrorism perpetrated by Trump (and continued by the current US administration) or the recent nuclear terrorism—as negotiating leverage.”

Zarif wrote that "possible indiscriminate human and environmental consequences of this international crime” meant that those behind it or involved as an “accomplice to this war crime…must not go unpunished.

The foreign minister reiterated Tehran’s willingness to again accept the limits on the nuclear program agreed in the JCPOA once the US returned to the deal and removed sanctions in a verifiable way. The US left the agreement in 2018 and imposed draconian sanctions on Iran, but the incoming Biden administration has said it wants to return to the agreement and is indirectly engaged in talks in Vienna to that end. The incident at Natanz underground enrichment facilities came with the Vienna talks due to resume Wednesday.

The Revolutionary Guards-affiliated Tasnim News Agency on Monday ran an editorial urging Iranian withdrawal from the talks. At a joint press conference with visiting US Defense Secretary Lloyd Austin on Monday, Israeli Prime Minister Benjamin Netanyahu said Israel would not allow Tehran to "obtain the nuclear capability to carry out its genocidal goal of eliminating Israel.”

Austin made no comment about Israeli involvement in sabotage at Natanz. The White House spokeswoman Jen Psaki denied any US role but did not condemn the attack and refused to comment on whether Israel was to blame.  She insisted the Biden administration was focused on the Vienna talks.

After Sunday’s incident, in contrast to previous cautious comments on attacks on Iranian nuclear facilities and assassinations of its nuclear scientists, Israeli media outlets including Kan Radio widely reported that the Israeli secret service Mossad had targeted the power generation system at Natanz, causing an explosion, fires and damaging some enrichment centrifuges. Zarif suggested in January that Israel wanted to sour prospects for Washington re-entering the JCPOA.