Iran starts enriching uranium to 60pc, its highest level ever Published On The announcement also marks a significant escalation after attack that damaged centrifuges at Natanz DUBAI (AP) — Iran began enriching uranium Friday to its highest level ever, edging closer to weapons-grade levels to pressure talks in Vienna aimed at restoring its nuclear deal with world powers after an attack on its main atomic site. A top official said only a few grams an hour of uranium gas would be enriched up to 60% purity — triple the level it once did but at a rate far slower than what Tehran could produce. International inspectors already said Iran planned to do so above-ground at its Natanz nuclear site, not deep within its underground halls hardened to withstand airstrikes.