In the flurry of diplomatic talk about North Korea, an ominous silence divides China and the United States on what they will do if the isolated nuclear-armed state falls into chaos, even collapse. Analysts believe North Korea's recent burst of rancour – this week threatening a new nuclear test –partly reflects its supreme leader Kim Jong-il's focus on controlling his succession, following illness that left the 67-year-old haggard and limping. Kim's declining health and a clutch of personnel changes in Pyongyang suggest the murky uncertainties of power in the one-party dynasty could drive North Korean behaviour in ways that test regional powers. The outside players with the biggest stake in North Korea's fate are the United States and its allies South Korea and Japan, as well as China, a neighbour and longtime benefactor of the Communist North. But if Beijing's leaders worry about the stability of their neighbour, they have not been sharing those fears with others. China has shrunk from talking with Washington about contingencies in North Korea, especially the risk that Kim's death or disability could push his state into turmoil, perhaps threatening the security of its small nuclear arsenal, according to analysts, officials and former officials who spoke to Reuters. “Certainly you get the feeling that they (China) are nervous about the situation in North Korea and that they must be doing some of their own contingency planning,” said Dennis Wilder, a visiting fellow at the Brookings Institution in Washington D.C. who worked in the National Security Council under President George W. Bush. “But this is not an area that they felt they had a lot of freedom to discuss.” There are no signs that Kim faces imminent death, or that his country is on the brink of turmoil. A controlled transition is possible. But the lack of a regional gameplan for his possible departure leaves the scenarios all the more uncertain and potentially volatile. “The stakes are so high that we'd all have to cooperate,” Shi Yinhong, an international relations professor at Renmin University in Beijing, said of the prospect of North Korean chaos. “But there's been no systematic discussion on what would happen and that's dangerous ... Impulses aren't enough, we'd need policies we agree on.” Not showing its cards China, the United States, South Korea and Japan have cooperated in stalled six-party talks seeking to coax North Korea to abandon nuclear weapons. Russia also participates. But these powers have divergent stakes in North Korea that would risk contention, even conflict, if the government there falters. The possibilities and many unknowns were spelt out in a study by Paul Stares, a security expert, and Joel Wit, a former US State Department official who dealt with North Korea, published by the New York-based Council on Foreign Relations in January. A relatively smooth transition to new leaders is “entirely plausible”, they wrote. But the potential for wrenching political upheaval “should not be summarily dismissed”, they added. Widespread starvation, outpourings of refugees, fragmentation of political and military control, and outright conflict are all potential problems that could emerge from such upheaval – and all with the North's primitive nuclear arsenal in the background. And the big players would all have rival interests in how to handle such trouble. South Korea states in its constitution that its government rules the entire Korean peninsula, and feels a union with its separated kin in the North is its right. Japan has been alarmed by North Korea's rocket launches and would share US worries about the security of its atomic weapons programme. But Seoul would be wary of Japan reasserting influence on the peninsula, write Stares and Wit. China has long regarded the North as a strategic buffer against the extension of US and allied forces up to its border, and it fears a surge of refugees pouring across its 1,416-km (880-mile) frontier with the North. Pushed by such fears, Beijing could send forces some way into the North, said Drew Thompson of the Nixon Center in Washington, who has been studying frontier relations between them. “China crossing the border again takes us back to the 1950s,” said Thompson, referring to the Korean War. The United States would be pulled by the need to secure North Korea's nuclear weapons, and pressure to help stem famine and a refugee exodus, wrote Stares and Wit. Little coordination But the regional powers have done little to work out how they would together handle these still distant but real risks. China fears disclosure of any talks over North Korea's future would ignite anger in Pyongyang, said John Park, a researcher at the United States Institute for Peace in Washington D.C. Beijing may also be reluctant to disclose its own intelligence and plans, however incomplete, Park added. “China may not want to show all its cards by engaging in discussions about contingency planning,” he said. A South Korean official, speaking on condition he was not named, said that he knew of no “significant exchange” between governments on the scenarios for North Korean instability. A researcher at a Chinese think tank said his country's military had plans to handle upheaval in the North. “But the diplomatic (policy) side hasn't been brought in,” added the researcher, who demanded anonymity to speak of sensitive policy issues. “There's also the lack of internal coordination which could be a problem.” Thompson said the risks were such that if a crisis erupted in North Korea then regional powers would probably “muddle” towards a coordinated response. “It would be much nicer if we had better communications, though,” Thompson said. “The possibilities are a minefield.”