STALLED DIPLOMACY

But it also takes Iran a significant technical step closer to the 90 percent concentration needed for bombs, explaining the West’s growing concern about the Islamic state’s stockpile of the material.

A U.S.-based think-tank, the Institute for Science and International Security (ISIS), this month said Iran would currently need at least two to four months to produce enough weapons-grade uranium for one nuclear bomb, and additional time to make the device itself.

Last week, Iranian officials said Tehran would negotiate on halting higher-grade enrichment if given fuel for the research reactor, in a possible attempt to show flexibility in stalled nuclear talks with world powers.

The IAEA said in its last report on Iran in late August that the country had doubled the number of centrifuges to 2,140 at Fordow since the previous report in May. More than 600 remained to be installed, the report showed.

Since then, diplomats said they thought Iran had put in place more centrifuges at the site near the holy Shi’ite Muslim city of Qom, about 130 km (80 miles) from Tehran and located deep under soil and rock for protection against any attack.

“They continue sort of unabated,” one envoy said.

But they said Iran was still operating the same number of machines as it has been since early this year, nearly 700 centrifuges.

It was not clear when the new equipment would be launched or whether Iran was holding back for technical or political reasons. It is also not known whether the centrifuges which are not yet operating will be used for 5 or 20 percent enrichment, or both, the diplomats say.