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Chinese President Xi Jinping's has assured US President Donald Trump that China had limited influence over North Korea, but that's only half true.
It's true that diplomatic relations between the two are weak. Xi has never visited Kim Jong Un in Pyongyang and Kim has never been to Beijing.
High ranking officials with ties to China in North Korea have been executed by Kim, sometimes with packs of dogs, sometimes with anti-aircraft guns.
But Gordon Chang, author of "The Coming Collapse of China," wrote in The Cipher Brief that 90% of North Korea's trade is done with China, including 90% of its oil and sometimes 100% of its aviation fuel. "China can disarm North Korea in the blink of an eye," he wrote.
And China can disarm North Korea by crippling its economy - but at a huge cost to the civilians of North Korea.
Sanctions on North Korea do not affect regular trade. Although the UN takes very seriously the prospect of an aggressive, nuclear-armed North Korea, economic warfare in the form of too-harsh sanctions certainly would wither and kill the poor, ordinary people of North Korea.
Additionally, China pressing North Korea to the point of regime collapse would contradict its interests, as Beijing doesn't want to face a strong, democratic, unified Korea on its borders that could play host to US military installations.