The world is watching closely to see what Beijing's response will be to North Korea's latest provocation, the shelling of a South Korean island in late November. China remains North Korea's only solid international ally – and a powerful one. For years Beijing has tolerated its neighbor's mercurial and often dangerous behavior, keeping the country afloat with fuel and food, protecting it from tough United Nations sanctions, and keeping it diplomatically engaged with the United States.
There is no doubt that "China is the single most influential country over North Korea," says Denny Roy, a North Korea expert at the East-West Center in Hawaii. Its potential leverage is such that Beijing could sink the North Korean government at will by cutting off vital supplies.