Diplomatic engagement has failed to stop North Korea's nuclear weapons program. Sanctions have been tightened with little result. And military force could be catastrophic.

So what can the world do to bring Kim Jong Un's renegade government into line? The answer may rest with China.

While Beijing's influence over North Korea appears to have diminished since Kim came to power in 2012, it remains its key trading partner. Experts says China could do more to restrict North Korean use of Chinese banks and limit supplies of food and fuel that provide an economic lifeline to Pyongyang.

Wednesday's purported hydrogen bomb test will intensify pressure on China to tighten the screws on Kim. It's been wary of doing for fear of causing the collapse of North Korea's socialist government.