Chinese curbs on exports of three niche metals to the U.S. have already rattled the market. Now, a bigger clampdown looks set to have far-reaching ramifications for supply chains feeding American defense and chipmaking industries.

Beijing this month slapped a ban on U.S.-bound exports of gallium, germanium and antimony in a tit-for-tat move in a technology trade war. The metals are important because they have crucial uses in many Western industries from military tech to semiconductors to satellites.

The ban may seem symbolic at first, given restrictions imposed more than a year ago had wiped out direct exports of Chinese gallium and germanium to the U.S. That pushed up prices and made it harder for traders to source buffer stocks. Yet panic levels are rising, because this time Beijing could crimp supplies further with rules prohibiting foreign companies and countries from helping U.S. manufacturers to evade the controls.