The US State Department policy of depending on China to influence the foreign and military policy of North Korea is based on an old obsolete understanding of Ko...rea as a tributary nation of China. This is called "Sadae Doctrine" in both North and South Korea, and regarded the root cause of demise of Yi Dynasty of Korea. The best and more realistic approach for the US is to scrap the Six-Party Talk (US, South Korea, North Korea, China, Japan, Russia) to dismantle nuclear wqeapon, and replace it with Three-Party Talk (US, South Korea, North Korea), and keep out Russia, China and Japan. Late Kim Il Sung told President Carter that blood is thicker than ideology and that anti-American public rhetoric is for the internal consumption. It is becoming more likely that South Korea and North Korea may take a joint military action against Japanese military expansion. Negative opinion against Vice President Biden who seems to put the US support on Japanese side, is beginning to surface among the opposition party members in South Korea. The conservative government of Japan is using the territorial dispute with Korea and China over two pieces of rock piles in the ocean to distract poublic attention away from Fukushima nuclear disaster, chronic economic stagnation, and to launch re-armament of Japanese Navy with offensive capability. In response, South Korea is producing more Aegis-class destroyers with anti-missile capability. China's major interest is to keep Korea divided as a geopolitical buffer zone against Japan and the US. For this reason alone, China will not tolerate unified Korea. Does the US understand this? Judging by what Vice President said and did, I am not at all sure. In 1950, China made it clear that China will intervene militarily if the American troops crossed the 38th parallel, indicating that if South Korean troops only crossed the line China would not intervene. The US crossed the line anyway and China intervened. A good proportion of population in Manchria are ethnic Koreans. They fought in the Korean War as a part of North Korean Army, not the Chinese Army. With the constant fear of revolt by Tibetans, Inner Mongolians and Turks, the ethnic stability of Manchuria should be a concern of China.