As the confrontation between North Korea and the United States deepens over Pyongyang's nuclear programs, China could play a critical role in defusing the crisis. But Beijing has taken few visible steps to push Pyongyang to give up its nuclear ambitions.

Foreign Ministry spokeswoman Zhang Qiyue says China is deeply concerned about the North Korean nuclear crisis, and is urging the two sides to talk out their differences and keep nuclear weapons off the Korean Peninsula. Ms. Zhang says Chinese officials are in close contact with Pyongyang. But the Foreign Ministry gave no details of any arguments, threats, or inducements Beijing is offering to help persuade North Korea to stop efforts to develop nuclear weapons.

China could put enormous pressure on North Korea if it wished to, because Beijing provides critically needed food and fuel to its impoverished communist neighbor. But analysts such as Xue Mouhong of Xi'an Jiaotong University say threatening or pressuring its long-time ally could backfire for China. "North Korea is very stubborn, you press them, they counter-press you," says Mr. Xue. "So there is no use to use pressure against North Korea, just talk."

But China has more influence over North Korea than any other country and Washington is sending two top-level delegations to Beijing in the next few weeks to enlist Chinese help in ending Pyongyang's nuclear programs. That will force China to choose between its communist ally or angering its largest trading partner, the United States. For China, either course could be costly.

China is the source of most of North Korea's oil imports and more than a third of its imported food. Professor Chen Fengjun of Peking University says major cuts in these supplies could cause serious problems. Professor Chen says those problems might include a "collapse of political power" in North Korea, which would seriously affect China.

Another analyst says chaos in North Korea could prompt up to one million starving North Korean refugees to flee across the border into northeast China. That would destabilize an area already plagued by high unemployment, poverty, and labor unrest.

China may also pay a price if it fails to take effective action against Pyongyang, because that might alienate Washington and sour the good relations that have been carefully cultivated by Chinese leaders for nearly two years.

Even worse from China's point of view, North Korea's nuclear program could prompt Japan and other Asian nations to develop nuclear bombs. A growing number of nuclear-armed neighbors would make China far less safe. But so far, China has only stressed its position that it does not want to see nuclear weapons on the Korean Peninsula. Beijing has not said how it can help accomplish that.

North Korea alarmed the world by taking steps in December to reactivate nuclear facilities at Yongbyon, which had been frozen under a 1994 deal with Washington. The country has since expelled U.N. monitors and declared it is quitting the global nuclear arms control treaty. Last week, the U.N. International Atomic Energy Agency decided to give the North "one more chance" to honor its international obligations, re-freeze the reactor, and re-admit the nuclear inspectors.