S enior Israeli officials are acknowledging that some enriched uranium may have survived the powerful U.S. strikes on Iran's key nuclear sites last month.

Pentagon reports Iran's nuclear facilities were "completely obliterated" in June strikes, offering a more optimistic assessment than earlier estimates while Iran acknowledges damage.

The process of uranium enrichment increases the concentration of U-235, an isotope that can sustain a nuclear chain reaction. Beginning in 2006, the U.N. Security Council called on Iran to suspend all uranium enrichment, but it endorsed the JCPOA on July 20, 2015.