China could stop North Korea's nuclear threat in a heartbeat without firing a shot

After a provocative North Korean missile launch in 2003, China completely cut off its supply of oil to North Korea for three days, and in no time the Kim regime caved to international demands and sat down for Six Party Talks on nuclear disarmament.

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.

But North Korea, with it's incessant nuclear provocations and near-weekly missile tests, functions as a giant bullseye to the US, though any military confrontation runs a high risk of going nuclear and killing hundreds of thousands, if not more.

"China will either decide to help us with North Korea or they won't," Trump said in an April interview with the Financial Times. "If they do, that will be very good for China, and if they don't, it won't be good for anyone."

So as North Korea progresses towards a nuclear missile that can strike the US, China must decide how hard it's willing to press the Kim regime, while considering its increasingly-strained relationship with the US for supporting a rogue regime.