Xi Jinping, the General Secretary of the Chinese Communist Party and the future president, ought to take the lead in restraining the irresponsible North Korean state, especially now that the rulers in Pyongyang have caused a third nuclear device to be detonated. Only Beijing, having hitherto given them limited yet vital support, has the clear and effective power to force a change toward prudence.
Unfortunately, the Chinese government will probably not take sufficient action until Kim Jong-un and his associates go even further. It should, however, not only increase sanctions on North Korea and decrease its remaining supports; it should also open the border to allow many of the people of North Korea to vote with their feet, accepting them at least temporarily as refugees, pending a change of regime.
On the one hand, China should stop supplying fuel to North Korea; on the other hand, it should relieve the North Korean people from even greater deprivation by letting them leave their homeland.
The Kim dynasty probably does not know how near they have come, by their relentless oppression, to acting upon the satirical advice that the playwright Bertolt Brecht (in a poem called "The Solution") gave to the East German Communists to "dissolve" the people and elect a new one – except of course that no people would accept the Kims' offer.
It is a bit encouraging that Global Times, a Chinese daily newspaper ultimately controlled by the Communist Party, with a populist or nationalist rather than a liberal bent, published an editorial in late January, saying that China would "not hesitate to reduce its assistance" to North Korea if it performs further nuclear tests, and that China should pursue its own interests, not Pyongyang's.
The Chinese Foreign Minister has rebuked the North Korean ambassador, and at the United Nations China will probably vote with the other members of the Security Council to somewhat tighten sanctions.
The incremental approach to North Korea is not working. China is the best placed power to avert an arms race in East Asia.