Billy Bishop says the US can easily pressure China to back then up on North Korea, simply by threatening to give nukes to South Korea and Japan. That's the one thing that will make China budge.
With that in mind:
NY Times - North Korea's nuclear arsenal threatens China's path to power. Decades of Chinese geopolitical strategy gets flushed down the poop chute if China pisses off the US.
Reuters - allowing nuclear weapons in Japan could defuse North Korean threat. The money shot:
“Just by raising this issue of nuclear principles, Japan will push the United States and China to act, and it is something that Beijing is not going to like,” said Takashi Kawakami, a security expert at Japan’s Takushoku University.And the dominoes fall like a house of cards. Checkmate.
“It’s the medicine that China needs to make it act against North Korea.”