China may have the most influence of any nation over Pyongyang, but North Korea's nuclear test illustrates the failure of Beijing's diplomatic approach, analysts say.
China has been North Korea's main ally for more than half a century, a relationship cemented in blood when Chinese troops fought alongside North Koreans against US and South Korean soldiers in the Korean War from 1950 to 1953.
But critics charge that China's ideological ties to the bankrupt communist state have blinded it to the danger posed by Pyongyang's atomic weapons ambitions.
"No country should be more embarrassed and more concerned than China," said Ralph Cossa of the Pacific Forum CSIS, a think tank in Hawaii.
Some analysts charge that North Korea would never have defied the international community to such an extent unless it was fairly confident that Beijing would protect it from the worst consequences.
Along with South Korea, China has argued against the hard-line response championed by Washington and Tokyo to North Korean brinkmanship during the three-year nuclear standoff.
China's efforts to curtail North Korea's nuclear ambitions have been in direct opposition to hardliners in the White House who are seeking regime change in Pyongyang.
Instead of sanctions or other tough measures, China has pushed for diplomatic efforts to persuade North Korea not to become a nuclear power.
Since 2003, China been the host of six-nation talks -- involving the two Koreas, China, the US, Japan and Russia -- that were aimed at reining in Pyongyang's nuclear program.
North Korea pulled out of the talks in November last year and China's pleas to Pyongyang to return to the diplomatic table have been ignored.
China is now presented with its biggest diplomatic challenge in years in deciding what to do about the nuclear test, said Shi Yinhong (
"It is under great pressure to line up with the US and take harsh sanctions against North Korea, while knowing that such a step could realize its worst nightmare -- the collapse of North Korea," Shi said.
Beijing has staked the legitimacy of its position on North Korea on promoting stability and economic progress in that country.
China is also worried about the potential flood of millions of North Korean refugees from over the border into its territory if Kim Jong-il's regime imploded.
With so much at stake for China, it is unlikely -- according to some analysts -- that China would back the US and Japan and fully support the kind of crippling sanctions that would bring about regime change in Pyongyang.
As well as being its chief political ally, China is the main provider of food and energy to the impoverished North.
"Even though China, I'm sure, is very upset and angry with what North Korea is doing, I'm still not sure China is really ready to cut off food and oil supplies and everything else to North Korea," said Brian Bridges, a political science professor at Hong Kong's Lingnan University.
A stern response from the UN Security Council would have to include tough sanctions if it were to send the correct message to North Korea and other countries that might be tempted to follow the Stalinist state's example, according to Cossa.
"We have been arguing for years, particularly in the last few years, that we really need to get together and provide a unified international response to North Korea," Cossa said.