The facility is a key choke point in Iran’s ambitions to speed up its nuclear work, as part of an effort to pressure the United States to suspend the sanctions President Trump has reimposed, and to convince Europe to compensate it for lost revenues as its oil revenue has dried up.
Secretary of State Mike Pompeo, who previously served as Mr. Trump’s C.I.A. director and ordered new operations to disrupt Iran’s nuclear progress, told the United Nations Security Council on Tuesday that Iran’s advanced centrifuges posed a threat.
“Iran is also accumulating dangerous knowledge,’’ he said, arguing for an extension of an arms embargo on Tehran that expires in October. “Late last year, Iran announced that its scientists were working on a new centrifuge — the IR-9 — that would allow Tehran to enrich uranium up to 50 times faster than the IR-1 centrifuges allowed” under the Obama-era deal.
David Albright, the president of the Institute for Science and International Security, a nonprofit group in Washington that tracks nuclear proliferation, said in an interview that a number of factors suggested the disaster was most likely an act of sabotage.
The existence of the facility was no secret: The Iranians promoted its opening in June 2018, and Mr. Albright’s institute described the plant in a report. The Iranians ran a glossy picture of it in a report last year.
The assembly plant, Mr. Albright said, was unlikely to have stockpiled the kinds of highly combustible materials that could generate a large explosion. The Iranian images of the plant released last year show the assembly of the centrifuges — tall, thin machines that enrich, or concentrate, uranium’s rare component, uranium 235.
Enriched to around 3 percent, the fuel can be used in nuclear reactors; at 90 percent, it can fuel atom bombs. Iran has insisted that its operations are entirely for civilian purposes, but both American intelligence assessments and a trove of documents stolen by Israel from an Iranian warehouse in January 2018 showed evidence of planning work on nuclear weapons.