The Chinese will end up tossing North Korea under the bus rather to endanger their trade
South Korea is an important trading partner with China and the rest of the world.
Should a crisis develop the US could refuse to pay bond debt to China and to redeem any bonds for the duration.
Trump and Kim are behaving like two kindergärtners paying with nukes in their sandbox -- a bad scenario. But most of this is foolish bluster. The adults are hopefully dealing with this.