ANALYSIS: TRUE. North Korea’s Nuclear Arsenal Threatens China’s Path to Power.

China’s path to dominance requires an American withdrawal and a message to American allies that they cannot count on the United States for protection. But North Korea threatens to draw the United States more deeply into the region and complicate China’s effort to diminish its influence and persuade countries to live without its nuclear umbrella.

At the same time, the strategic location of the North — and its advancing nuclear capabilities — makes it dangerous for China to restrain it.

“North Korea may not be the biggest problem to China, but it does add a unique and very serious dimension to China’s task of supplanting America in East Asia,” said Hugh White, a former strategist for the Australian Defense Department. “That’s because it is the only East Asian power with nuclear weapons.”

Even if the United States steps back from the region, Mr. White added, “North Korea’s capability means China can never be able to dominate the region as much as its leaders today probably hope.”

The time for China to rein in its erratic ally was yesterday, but Beijing still thinks they can have it all.