VIENNA — Iran has laid groundwork for new centrifuges that would allow it to expand uranium enrichment at a fortified underground bunker but lacks key equipment needed to operate them because of sanctions, a senior U.S. official told NBC News on Saturday.
The official referred to the nuclear facility as a "Potemkin" plant, a facade that could not operate and was under close watch by the International Atomic Energy Agency.
The official commented after a report from The Associated Press that Iran had put finishing touches for the installation of thousands of new-generation centrifuges at the cavernous facility — machines that can produce enriched uranium much more quickly and efficiently than its present machines and could help it build a nuclear weapon.
But the diplomats also told the AP that while the electrical circuitry, piping and supporting equipment for the new centrifuges was in place at the Fordo facility, Iran had not started installing the new machines, and they could not say whether it was planning to.
Still, the senior diplomats — who asked for anonymity because their information was privileged — suggested that Tehran would have little reason to prepare the ground for the better centrifuges unless it planned to operate them. They spoke in recent interviews — the last one Saturday.
The AP said the reported work at Fordo appeared to reflect Iran's determination to forge ahead with nuclear activity that could be used to make atomic arms despite rapidly escalating international sanctions and the latent threat of an Israeli military strike on its nuclear facilities.Story: What would happen if Iran did get the bomb?
Fordo could be used to make fissile warhead material even without such an upgrade, the diplomats said.
They said that although older than Iran's new generation machines, the centrifuges now operating there can be reconfigured within days to make such material because they already are enriching to 20 percent — a level that can be boosted quickly to weapons-grade quality.
Their comments appeared to represent the first time anyone had quantified the time it would take to reconfigure the Fordo centrifuges into machines making weapons-grade material.Video: US cautiously optimistic over potential Iran talks (on this page)
In contrast, Iran's older enrichment site at Natanz is producing uranium at 3.4 percent, a level normally used to power reactors. While that too could be turned into weapons-grade uranium, reassembling from low to weapons-grade production is complex, and retooling the thousands of centrifuges at Natanz would likely take weeks.
The diplomats' recent comments came as International Atomic Energy Agency inspectors are scheduled to visit Tehran on Sunday. Their trip — the second this month — is another attempt to break more than three years of Iranian stonewalling about allegations that Tehran has — or is — secretly working on nuclear weapons that would be armed with uranium enriched to 90 percent or more.Strait of Hormuz: Iranians, smugglers and fireworks
Diplomats accredited to the IAEA expect little from that visit. They told the AP that — as before — Iran was refusing to allow the agency experts to visit Parchin, the suspected site of explosives testing for a nuclear weapon and had turned down other key requests made by the experts.
Iranian officials deny nuclear weapons aspirations, saying the claims are based on bogus intelligence from the U.S. and Israel.
But IAEA chief Yukiya Amano has said there are increasing indications of such activity. His concerns were outlined in 13-page summary late last year listing clandestine activities that either can be used in civilian or military nuclear programs, or "are specific to nuclear weapons."
This article contains reporting from NBC News' Andrea Mitchell and The Associated Press.