Progress in communication between North and South Korea on Saturday prompted concern in the Japanese government that Seoul may rush into dialogue with the North at the expense of the pressure campaign espoused by Japan and the United States.
"South Korea might run off ahead on a course of dialogue," a senior Foreign Ministry official said in the wake of talks in Seoul between South Korean President Moon Jae-in and a high-level North Korean delegation sent to attend the opening ceremony of the Pyeongchang Winter Olympics the day prior.
The delegation gave Moon a letter from North Korean leader Kim Jong Un inviting him to visit the North, a day after Prime Minister Shinzo Abe said he and Moon had affirmed their shared stance of maximizing pressure on Pyongyang until it scraps its nuclear program.
Defense Minister Itsunori Onodera told reporters in Saga Prefecture that dialogue between the two Koreas must be "based on the premise that North Korea will change its basic nuclear and missile policies."
Officials in Tokyo suspect North Korea is trying to chip away at the united front of the United States and its East Asian allies as international sanctions bite the hermit country. Japan's focus is now likely to be on fortifying trilateral cohesion with South Korea and the United States.
The Abe administration is in favor of maintaining the diplomatic and economic pressure campaign regardless of the thaw between the two Koreas over the Olympics, arguing that yielding to dialogue on North Korea's terms would mean effectively accepting it as a nuclear power.
"North Korea seems to have no intention of abandoning its nuclear (program)," a Japanese government official said.
While Tokyo has not condemned recent talks between the two Koreas insofar as they concern participation in the Pyeongchang Games, Abe warned Moon during their Friday meeting against North Korea's "smile diplomacy."
North Korea's overtures to the South have included sending as part of its delegation Kim Yo Jong, the current leader's younger sister, who is thought to be one of his closest aides.
"It's clear to see that Kim Jong Un's agenda is to get a dialogue offensive under way," a Japanese government source said.
"By sending the sister to South Korea and seeking a visit by the president, North Korea is probably trying to give the impression that it's taking the lead on dialogue," another source close to the government said.
According to a diplomatic source, some in the Abe administration "would not oppose the very idea of talks" between Moon and Kim "if they would entail (Moon) pressing North Korea to denuclearize."
But most, a source close to the prime minister's office said, feel that "dialogue is meaningless unless North Korea says it will abandon nuclear weapons in a verifiable and irreversible manner."