"Chinese leaders wants to avoid a strong, US-aligned Korea on its borders. They want to prevent a massive refugee outflow from a crushed North Korean state. And they want to defuse the Korean peninsula's nuclear tensions - but in doing so, they'd expose an ugly truth.
US President Donald Trump has accused China of refusing to help with North Korea.
If China unilaterally denuclearized North Korea to head off a US strike, this would only vindicate that claim, and raise questions as to why China allowed North Korea to develop and export dangerous technologies and commit heinous human rights abuses.
For China, it's "not even about saving" the approximately 25 million living under a brutal dictatorship in North Korea, but rather maintaining its buffer state, according to Tack.
China would likely seek to install an alternative government to the Kim regime but one that still opposes the West and does not cooperate with the US.
According to Tack, China needs a North Korean state that says "we oppose Western interests and we own this plot of land."
If China doesn't exert its influence soon, it may be too late."
http://www.businessinsider.com/china-response-us-first-strike-north-korea-2017-3