Your are right this will not go very but for different reasons. It's the US and the South Korean who have not lived up to the armistice agreement which clearly stated :"All foreign troops have to leave Korean soil". I doubt he US will give up the advantage of having Nuclear weapons stationed that close to he Chinese Mainland and now have a missile shield for protection installed as well. The Chinese under those circumstances see no reason to pressure North Korea into a more peaceful attitude. Too bad that they did not let the Koreans work it out themselves before the North had developed the bomb. Kind of late now.