Among several new types of sanctions against North Korea being pushed by the US is a full-scale oil blockade. Such a blockade would necessarily have to run through China, with its oil pipeline into North Korea. But the idea puts China in a tough position.
China’s President Xi Jinping has been keen to show himself to be cooperating on North Korea, despite US officials often blaming them for the lack of progress. On the other hand, giving in to increasing US demands without getting anything in return would be very unpopular.
Xi’s strategy initially was to support US sanctions efforts in hopes it would also get the US to accept his diplomatic efforts. Not only has this not happened, but the Trump Administration has grown increasingly publicly hostile to diplomacy in general.
So now when the US comes along looking to get an oil embargo, Xi is faced with either looking suddenly uncooperative, or looking like he’s letting the US walk all over him by letting them continue to spurn diplomacy in favor of more sanctions.