The report concluded that as of early this month, Iran had made 630 kilograms, or about 1,390 pounds, of low-enriched uranium.

Several experts said that was enough for a bomb, but they cautioned that the milestone was mostly symbolic, because Iran would have to take additional steps. Not only would it have to breach its international agreements and kick out the inspectors, but it would also have to further purify the fuel and put it into a warhead design — a technical advance that Western experts are unsure Iran has yet achieved.