The federal agency has a broad mandate to protect Americans’ health and an expansive global reach. But the COVID-19 pandemic has been one of its most daunting challenges.

Tariffs have been applied over the years to protect homegrown industries and target competitors who are seen as using unfair trade practices. They impose costs on both importers and exporters and had been in decline until the recent U.S.-China trade war.

Tens of millions of Chinese now identify as Christians, and the number has grown rapidly, posing challenges for a government that is officially atheist and wary of threats to its power.

The Muslim separatist group, based in the Xinjiang province in northwest China, presents a heightening security challenge for Beijing.