An item on page 3 of the current edition (No. 1519) of Private Eye in the UK and headlined "Money talks" touches on this.

The article ends with this paragraph: "WHO's kow-towing might just be related to its own precarious financial position, which makes it increasingly reliant on Beijing. Recent figures show that the US, nominally WHO's largest funder, is late with its two latest annual fees, owing almost $100m as part of a general withholding and delaying of payments to UN agencies. China, second-largest contributor, is more reliable."

Edit to add: Private Eye is a fortnightly news magazine, bitingly satirical in parts, and renowned for its dogged campaigning. Wikipedia: https://en.wikipedia.org/wiki/Private_Eye