Japan's visit to North Korea comes after broad regional agreement that Pyongyang should not be offered talks unless it displays a genuine commitment to denuclearization.
A small crack has appeared in the international show of unity against North Korea's development of nuclear weapons, following the "secret" visit to Pyongyang this week by a special adviser to Japan's prime minister, Shinzo Abe.
Isao Iijima arrived in the North Korean capital on Tuesday for a four-day visit that many believe was aimed at restarting talks on the regime's cold war abduction of Japanese citizens, who were used to train communist agents.
Tokyo's decision to engage with the North was apparently known initially to only a handful of officials at the prime minister's office; Tokyo had not even notified its regional partners of Iijima's plans, to the barely concealed irritation in Seoul and Washington.
"We don't think Isao Iijima's visit to North Korea was helpful," South Korean foreign ministry spokesman Cho Tae-Young said.
Glyn Davies, the US special representative for North Korea policy, was more ambiguous. Asked about the visit, he told reporters in Tokyo. "I think we have some days to wait, all of us, before we know if there are any results from this mission.
"We all have fundamental security interests in dealing with North Korea ... it is important that we stay connected very closely."
Abe refused to comment on the purpose of Iijima's visit, but it has become apparent that Tokyo has spied an opportunity to make progress on a subject close to the prime minister's heart – the abduction of 17 Japanese citizens by North Korean agents between 1977 and 1983.
Koizumi secured the release of five abductees, while Kim said that eight of the remaining 12 had died and the others had not been abducted – claims that Tokyo refuses to believe.
The abductions are the biggest single obstacle to the resumption of diplomatic ties between the two countries.
Abe has remained in close contact with the families of the missing abductees and has made it a personal mission to secure their release, or at least obtain reliable information about their fates.
"We can safely assume that given Shinzo Abe's long-standing interest in the abduction issue, Iijima's top priority is to see if Pyongyang can send back another group of abductees," a government official in Tokyo told the Monitor on condition of anonymity.
Abe told a parliamentary committee this week that he would consider a summit with the North's leader, Kim Jong-un, if it meant making demonstrable progress on the abductions and Pyongyang's nuclear weapons program. "If summit talks are important measures in resolving the abduction, nuclear, and missile issues, we should naturally consider them," he said.
The official in Tokyo, however, said an imminent breakthrough was unlikely. "I don't think there is a mood of optimism. It is still very much a matter of wishful thinking. But Iijima's visit at least shows the nation that Abe is willing to go much further than his [Democratic Party of Japan] predecessors."
Abe is aware, too, that even the faint promise of good news on the abductions will bring political dividends, just two months before the upper house elections. The popularity that propelled him into the prime minister's office the first time round owed much to his close personal association with the abductees' families.
For many years, the abductee issue has been such a highly emotional issue in Japan that no politician could afford to ignore it. During the now-moribund six-party talks on North Korea's nuclear ambitions that began in 2003, Japanese negotiators raised the abductee question even when it seemed irrelevant to other parties – the US, China, Russia, and South Korea.
"[The abductions issue] is one topic of discussion that can get Japan's attention regardless of other sources of tension and sanctions," said NightWatch, a newsletter that tracks and assesses threats to US national security, adding that the simple fact that the two countries were talking "begins to look like a thaw. It is entirely tactical, but better than threats."
Given the irritation in Seoul over Iijima's visit, the official in Tokyo agreed that Japan's priority is "not to break the united front" against North Korea that has emerged in the wake of the regime's recent threats against the US, South Korea, and Japan.
Iijima, who was due to fly to Beijing from Pyongyang on Friday evening, rarely talks to the media and is unlikely to divulge any details. He is known to have held talks with the regime's second in command, Kim Yong-nam, and with Kim Yong-il, a senior official in the central committee of the ruling Korean Workers' Party.
Pyongyang's intentions are similarly opaque. The country's official KCNA news agency said only that Iijima, who visited Pyongyang with Koizumi in 2002 and 2004, was met at the capital's airport by North Korean foreign ministry official Kim Chol-ho.
But in an article in South Korea's Hankyoreh newspaper, Jeong Nam-ku speculated that the impoverished North was angling for concessions in return for offering new information about the abductees.
Citing a report in the Rodong Sinmun, the official paper of North Korea's ruling party, calling on Japan to "adopt a rational approach" to outstanding issues, Jeong said: "This suggests that Pyongyang views it as necessary to tie any negotiations with Tokyo on the abductee issue to discussion of normalizing diplomatic relations."
In Tokyo, the chief cabinet secretary, Yoshihide Suga, dismissed suggestions that Japan had unwittingly fallen for a ploy to divide the region. Responding to Seoul's criticism, he said:" "I don't understand what South Korea is trying to say."
There has been broad agreement among the US and its partners in the region that North Korea should not be offered talks unless it displays a genuine commitment to denuclearization.
Japanese officials, though, were divided on the merits of Iijima's trip. Kyodo quoted an unnamed foreign ministry official as saying that the adviser's presence in Pyongyang had allowed North Korea to "proclaim to the world that it is not isolated in the international community."
"With the otherwise secret North Korean visit by Iijima broadcast throughout the world, Japan has been tripped up by North Korea," the official was quoted as saying.