New Delhi, Oct. 21 -- But this technological force multiplier has come with an unsettling vulnerability: Ukrainian drone makers are highly dependent on electronics made by China, a key Russian ally.

Ukraine's greatest fear is that the Chinese government could severely restrict its access to these critical parts. It also worries that Russian defense companies that need these same supplies could be given preferential treatment by Chinese factories.

Over the past two years, Ukraine has sought to break its dependence on China by expanding domestic manufacturing and importing more supplies from Taiwan, Europe and the U.S. That has minimized its need for Chinese-made electric motors, flight controllers and other parts.

Yet Ukraine cannot ent...