The president-elect’s pledge to use tariffs to stem the flow of opioids from China could backfire if Beijing responds by ending counternarcotics cooperation.

The tariff threat is rattling China's industrial complex, which sells goods worth more than $400 billion annually to the US

China's state media warned U.S. President-elect Donald Trump his pledge to slap additional tariffs on Chinese goods over fentanyl flows could drag the world's top two economies into a mutually destructive tariff war.