DUBAI, United Arab Emirates—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 percent 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. The move is likely to raise tensions even as Iran negotiates in Vienna over a way to allow the United States back into the agreement and lift the crushing economic sanctions it faces. However, its scope also provides Iran with a way to quickly de-escalate if it chose. …