"If a deal is not reached, I will have no other choice but to put high levels of taxes, tariffs, and sanctions on anything being sold by Russia to the United States and other participating countries," President Donald Trump posted on his social media platform Truth Social.
There is such a thing as secondary sanctions, IE sanctioning a country that does business with a sanctioned country, and that’s precisely what China has been threatened with if they do business with Russia.
And Russia’s economy is the same size as some US states, so China would much rather stay on good terms with the USA.
Trump likely wants to do a full blockade on China anyway, so them helping Russia - which they are clearly doing unofficially - would be an excuse to do that.