https://www.wsj.com/articles/fentanyl-crisis-fed-by-flow-of-chinese-chemicals-to-mexican-cartels-11671722056

Sour U.S.-China Relations Feed the Fentanyl Crisis

A few years ago, a joint effort to limit the flow of illicit fentanyl was a successful point of collaboration in a tense U.S.-China relationship. In 2018, China restricted the production and sale of two of the most common ingredients for the drug, a move that won it praise from the U.S.

Since then, the U.S. has adopted a tougher posture toward China, while China has also grown more assertive about defending its interests.