Huawei Technologies Co. alarmed politicians from Washington to Tokyo when it took the wraps off a $900 smartphone that signaled China’s rapid advance in semiconductor technology. The episode also thrust the little-known company that made the chip for Huawei into the middle of the US-Chinese battle for geopolitical supremacy.

Semiconductor Manufacturing International Corp. has emerged as Beijing’s secret weapon in breaking through a US-organized blockade aimed at containing China’s technological progress, despite years of American sanctions. Its success in delivering an advanced, 7-nanometer processor to Huawei set off jubilant celebration at home, and triggered partisan finger-pointing in Washington over the apparent failure.