New Delhi, July 10 -- BEIJING - China imposed an immediate ban on helium exports Friday, citing renewed military conflict in the Middle East, deepening an already fragile supply crunch for the gas that underpins every stage of modern semiconductor manufacturing.

China is not a helium producer. It imports more than 85 percent of its supply, with Qatar the dominant source and Russian re-exports the secondary channel. Beijing had carved out a significant role as an intermediary trader, routing Russian helium to European and Asian customers. That role stopped Friday when the export ban took effect.

The timing was exacting. The ban landed as the third consecutive week of tanker disruptions in the Strait of Hormuz continued to compress Qatari...