IN their coordinated efforts to force North Korea to give up its nuclear ambitions, the United States, Japan, and South Korea have had an effective, if largely silent partner: China.
"They have made it very clear that they do not want a nuclear capacity on the peninsula," says a senior administration official, who has consulted directly with Chinese leaders about the matter. "They do not want North Korea to have the bomb."
In what some analysts see as a model of how collective security can work in the post-cold-war era, Washington, Tokyo, and Seoul have cooperated in placing political and economic pressure on Pyongyang, even hinting at preemptive military action if steps are not taken by North Korea to reverse its nuclear course.
But largely silent during two years of carrot-and-stick diplomacy has been China, a regional giant that could have much to lose if North Korea completes a nuclear reprocessing facility that could soon turn out plutonium to build a nuclear bomb.
Despite its low profile, China has quietly weighed in, adding to the pressure that earlier this year prompted North Korea to agree in principle to open its nuclear facilities in Yongbyon, near Pyongyang, to international inspection, the US official says.
"They cannot do these things publicly," the official says. "But in their own way they've been helpful."
In November, China's foreign minister made the most forceful statement yet that nuclear weapons on the Korean peninsula would not be in China's interest.
State Department officials say Qian Qichen's remarks reflected a longstanding Chinese concern that the introduction of nuclear weapons in the peninsulas would be a destabilizing factor in the region.
Tactically, China's position remains that dialogue, not pressure, is the way to deal with North Korea. "We do not wish to see any international pressure," Mr. Qian told reporters in November.
One reason for China's reticence is that North Korea is its remaining ideological ally in Asia and a close trading partner. North Korea has also become a major conduit for the reexport of Chinese weapons.
But analysts detect a slight public stiffening of China's position on North Korea's nuclear program which they attribute to a number of factors. One is China's own recently announced readiness to sign the nuclear non-proliferation treaty.
"We believe that with this decision, China adopted a firmer stance, pressing North Korea to implement IAEA [International Atomic Energy Agency] safeguards," Arnold Kanter, undersecretary of state for political affairs, told a Senate committee in February.
Another is the gradual shift in China's economic and political relations with the two Koreas. Trade and economic assistance to the North have declined even as economic ties with the South have been strengthened.
Qian's November statement was also seen as a means of reducing pressure in Congress to revoke China's most-favored-nation (MFN) trading status with the US.
Despite the small but perceptable shift in China's position, critics of the US's cautious policy of "constructive engagement" toward Beijing fault the Bush administration for settling for less than a full-court press by China on the Korea nuclear issue.
"It's pretty obvious that if one country could exert enough pressure on [North Korean president] Kim [Il Sung] to end his nuclear ambitions it would be China," says Richard Fisher, an East Asia expert at the Heritage Foundation. "Given the resources available to China ... they're not doing as much has they could."
The US and South Korea have made significant concessions to convince North Korea to abandon its nuclear weapons program, including Washington's unilateral decision last year to remove all of its nuclear weapons from South Korea.
Japan, meanwhile, has told North Korea that it will have to admit international inspectors before relations with Tokyo can be normalized.
Japan has indirectly linked normalization and financial aid to Pyongyang's willingness to abandon construction of its reprocessing facility. Experts say the plant could be completed as early as June, putting North Korea within six months of having its first nuclear bomb.
North Korea ratified an inspections agreement last month. The senior official says it is too early to tell whether ratification is merely a ploy to buy time to complete the reprocesssing plant or an indication of good faith on the nuclear issue.
"It's too soon to know whether they're hiding something or moving forward," says the official. But noting a recent press interview in which Kim Il Sung stressed his determination to improve relations with Washington, the official adds: "There's a whole lot of rhetoric in there that, if believeable, would tend to make you say yes, that they're moving forward."