USA Today reports: "North Korea is among the most isolated and sanctioned countries on the planet. And yet it still somehow has enough cash to develop a nuclear weapons arsenal capable of threatening much of the eastern Pacific and, some day, the United States. The reason is simple. The regime of Kim Jong Un continues doing $5.3 billion in business each year — 85% of its trade — with China. Amid rising tensions and the threat of war, the best way to force North Korea to curb its nuclear ambitions is if China brings its considerable economic leverage to bear...The Kim regime has already responded with angry, rhetorical darts in recent days — evidence of just how much clout the Chinese carry. That's a start. But China could also: 

• Favor a Security Council resolution restricting oil to North Korea, a true lifeline for the hermit kingdom, which has one refinery along the Yalu River border with China. The idea has gained traction within China, where the state-controlled Global Times has urged leaders to take this step should North Korea continue its nuclear or missile testing.
• Aggressively prosecute Chinese companies that funnel advanced technology for long-range missiles or uranium-enriching centrifuges into Kim's regime. North Korean rocket boosters that fell into the sea after a successful launch last year were scooped up by the South Korean navy and found to contain transmitters, circuity and specialized pressure sensors made by Western countries. They were shipped to North Korea by Chinese distributors, according to a Washington Post report. Eighty percent of foreign goods flowing into North Korea run through Chinese companies. That has to stop. 
• Crack down on Chinese financial institutions that launder North Korean purchasing money, much of it illegally acquired through drug dealing, counterfeiting and arms sales."