China's race to stop the spread of COVID-19 is clogging highways and ports, stranding workers and shutting countless factories — disruptions that are rippling through global supply chains for goods ranging from electric vehicles to iPhones.

While some factory owners try to tough it out through "closed loop" management that keeps workers isolated inside, some said that is becoming harder to sustain given the extent of local COVID-19 curbs aimed at heading off the omicron variant, complicating efforts to procure materials or ship products.

Foxconn Interconnect Technology, a unit of Taiwan-based Foxconn that makes data transmission equipment and connectors, has kept a plant open in Kunshan, which borders Shanghai, in a closed loop but is only able to run at 60% of capacity, a person familiar with the matter said.