Kim Jong-il, the dictator of North Korea, took the trouble to manifest himself at the Pyongyang airport on Sunday to greet the Premier of China, Wen Jiabao. This rare sign of respect offers some ray of hope that Mr. Wen will be able to exert influence to restrain North Korea's nuclear-weapons program.
After a North Korean nuclear warhead was detonated underground in May, China supported a tightening of UN sanctions, three weeks later. Reportedly, the Chinese are from time to time closing their border crossings with North Korea, thus constricting an overwhelmingly large portion of North Korea's foreign trade. Some observers think the rulers of North Korea are taken aback by the degree to which the Chinese are actually adhering to the sanctions.
A Chinese-government-owned English-language newspaper, China Daily, cites experts as saying that Beijing would not have sent such a high official as Mr. Wen to Pyongyang, unless it wanted to make progress on the nuclear-weapons issue, though the visit's ostensible purpose is to celebrate the 60th anniversary of diplomatic relations.
So far, the North Korean Prime Minister, confusingly named Kim Yong-il (but not a relative of Kim Jong-il), has said during Mr. Wen's visit that his country is open to "bilateral or multilateral dialogue" on the nuclear question, not making clear whether that means a resumption of the six-party talks that last took place in 2007.
To all appearances, China does not want to press the rulers of North Korea so hard that their regime collapses, causing a huge influx of economic refugees into China, and perhaps bringing to an end a useful buffer state. On the other hand, if the North Korea nuclear program goes any further, it is likely to provoke an arms race in East Asia, specifically a military buildup by Japan and South Korea that would be extremely undesirable in Beijing's eyes, changing the regional balance of power.
Though the North Korean ruling elite seems to be preoccupied with extracting some sort of acknowledgment from the United States, China is the power that has the greatest practical influence with North Korea, not only because of the long land border between the two countries, but even more by means of its enormous trade surplus with North Korea, which amounts to foreign aid.
Mr. Wen could and should do a great deal for the cause of nuclear non-proliferation on his three-day visit to Pyongyang.