While a territorial dispute threatens to drag China and Japan into conflict, a separate, slow-motion crisis building on the Korean peninsula could further inflame their rivalry.
Evidence North Korea is about to pull the trigger on its fourth nuclear test underline that the North is marching determinedly, one step at a time, toward the day when it can target any city in the Asia Pacific--and potentially large population centers in the U.S.--with nuclear attack.
South Korea's Foreign Minister Yun Byung-se last month called the fourth test a potential 'game-changer.'
True, a fourth test will add pressure on the U.S. to bolster its missile defenses in the region--and it could bring South Korea and Japan closer to contemplating their own nuclear deterrents, separate from the U.S.
This is China's nightmare: a nuclear arms race on its doorstep, and one that adds muscle to its rival Japan as the two wrangle over a set of islets in the East China Sea.
But will China's leaders act? 'They are looking at North Korea increasingly as a strategic liability rather than an asset,' says a senior South Korean Foreign Ministry official.
Beijing, he says, is alarmed at North Korea's direction under Kim Jong Un, a novice dictator with a short-back-and-sides hairdo who has shown the world his ruthless side by executing his own uncle.
Yet it would be a huge leap for Beijing to actually abandon one of its few real friends in the world.
No other country has more influence on North Korean behavior: Without Chinese food and oil, the North Korean economy might collapse. But that's likely not an outcome Beijing desires, even though the execution in December of Jang Song Thaek robbed Beijing of one of its best friends in Pyongyang. China still values North Korea as a buffer against U.S. forces stationed in South Korea, and it fears that a messy implosion of a nuclear-armed regime could spill chaos over its borders.
In the end, the demise of a socialist ally may be too unnerving a prospect for the Chinese Communist Party, which frets about its own mortality.
And those calculations are what may embolden Pyongyang to keep going with its nuclear tests.
'They know that China will not go beyond strong rhetoric,' says Chun Yung-woo, a former national-security adviser to the South Korean president who was speaking at the recent Asan Plenum in Seoul that brings together some of the world's top strategic thinkers on Asia.
North Korea likely possesses a handful of crude nuclear bombs. A report from the think tank 38 North, affiliated with Johns Hopkins University, says North Korea conducted at least one engine test of what is likely a road-mobile intercontinental ballistic missile in late March or early April.
Once Pyongyang manages to miniaturize a nuclear device to sit on top of a rocket, half the planet's economy in the Asia Pacific and more than half of its people will be at the mercy of Mr. Kim.
One comforting thought is that North Korea may be years away from acquiring that capability. And even if Mr. Kim is eventually able to deliver a nuclear bomb accurately, he likely won't because he knows that his recalcitrant nation instantly would be reduced to ashes. In other words, he'll choose regime survival over suicide.
Still, none of the carrot-and-stick tactics adopted so far to stop Mr. Kim have worked.
Over the years, North Korea and its immediate neighbors, along with the U.S., have huddled periodically in so-called 'six-party talks' to try to find a way around the impasse. Among other inducements to get Pyongyang to change course have been the prospect of security guarantees, support to develop a peaceful nuclear energy program, and even the possibility of a U.S. presidential visit.
But those talks are now on ice. From Pyongyang's perspective, nuclear weapons are its ultimate protection against attack aimed at regime change; it has taken to calling them a 'treasured sword.'
The U.N. has imposed stern sanctions on North Korea, and the U.S. applies additional unilateral ones.
Yet sanctions so far have had only limited impact on a country that operates on the outlaw margins of the international economy, relying for hard currency on the exports of arms, narcotics and fake bank notes. By comparison, Iran is more integrated into the global economy and feels the punishing effects of sanctions more keenly. Life in Pyongyang, in fact, may even be improving.
If North Korea goes ahead with a fourth test, as seems inevitable, more sanctions will follow, possibly targeting North Korean financial flows as well as Kim family money, if it can be identified. There's a chance that Mr. Kim might flinch if his lavish lifestyle was threatened, and he could no longer buy the loyalty of Pyongyang's elites, or fund his military fantasies.
Of course, it's always possible the regime may collapse. It has to be assumed that many senior officials fear for their lives after the execution of Mr. Jang, which has exposed cracks in a government that once appeared monolithic.
But don't count on an uprising against Mr. Kim who has been surprisingly efficient at consolidating his control over the military since taking over as leader after his father, Kim Jong Il, died in December 2011.
'We'll have to live with him whether we like him or not,' says Mr. Chun, the former national-security adviser, who calls Mr. Kim 'more reckless, more ruthless and more dangerous than his father.'
世界上没有第二个国家对朝鲜所做行为的影响超过中国：如果不是中国不向朝鲜提供食物和石油，朝鲜经济可能会崩溃。但北京或许并不希望看到朝鲜经济崩溃，尽管朝鲜在去年12月初处决张成泽(Jang Song Thaek)使中国政府失去了一个老朋友。中国仍将朝鲜视为针对驻韩美军的一个缓冲器，而且中国担心拥有核武器的朝鲜如果发生内乱，可能导致由此引发的混乱局面波及中国。
朝鲜可能拥有少量粗制核弹。约翰•霍普金斯大学(Johns Hopkins University)附属的智库38 North发布的一份报告称，朝鲜似乎已经在3月底或4月初进行了至少一次陆基机动洲际弹道导弹引擎测试。