Tensions between the U.S. and China are higher than ever, as president Trump increased the Chinese tariffs from 10% to 25% without any warning. China is still willing to continue the negotiations, but AMD and Nvidia investors fear that negotiations could fail and the companies may eventually be locked out of the Chinese market.
https://www.notebookcheck.net/Trump-increases-tariffs-for-China-AMD-and-Nvidia-could-be-in-trouble.420298.0.html
I find it strange because China could only ban products its capable of substituting, and graphic cards are not such products.