North Korea took advantage of a slight disarray among Japan, South Korea and the United States to shake up the partnership.

Unless the three partners remain constantly alert to such ploys by Pyongyang and strengthen their ties, they will never defuse the situation.

While North Korea continues its nuclear and missile development programs in disregard of condemnations from the international community, South Korean President Moon Jae-in on July 17 took the initiative to propose full dialogue with North Korea.

If the proposed North-South dialogue can improve relations on the Korean Peninsula, that, in itself, would be desirable from the standpoint of securing regional stability.

But judging by the reactions of Tokyo and Washington right after Moon made the proposal, there was little indication that Seoul had laid the sufficient groundwork to get its two partners fully on board.

North Korea's threat is growing, what with the ICBM missile launch earlier this month. The Moon administration should have explained its intention thoroughly to all nations concerned, particularly to Japan and the United States, before taking action.

Seoul called for top-level North-South military talks as well as Red Cross discussions.

With regard to the military talks, Seoul apparently intends to include on the agenda something the Pyongyang leadership would not be happy about--suspension of propaganda broadcasts around the Demilitarized Zone.

As for the Red Cross talks, Seoul intends to propose the resumption of a program for reuniting families separated across the border. The program has kept Pyongyang edgy about any information reaching it from the outside.

These two proposals are based on a message Moon directed at North Korea in his speech on July 6 in Berlin, the city that symbolizes German reunification.

In the speech, Moon called for dialogue on not only nuclear issues, but also all matters of interest to North Korea, including the conclusion of a peace treaty sought by Pyongyang.

Moon reminded us strongly of the late Kim Dae-jung, who preached peaceful coexistence 17 years ago in Berlin. At the time, North Korea indicated reluctance, but Kim's effort eventually bore fruit in the first North-South summit.

To be sure, Moon's proposal has to do with matters that are of specific relevance to Koreans, and they are not in conflict with sanctions approved by the U.N. Security Council.

Still, there is no question that Moon has created subtle ripples in the Japan-South Korea-U.S. partnership.

White House press secretary Sean Spicer appeared cool to the proposal, indicating that conditions were not yet right for dialogue with Pyongyang.

While the Japanese government was not pleased with Moon's going solo in making the proposal, Chief Cabinet Secretary Yoshihide Suga stopped short of expressing displeasure.

"We do not think (Moon's action) will cause any problem to the Japan-South Korea-U.S. policy of applying stronger pressure on North Korea," he simply said.

The important thing for Tokyo, Seoul and Washington is that while they must remain on the same page to keep applying pressure on Pyongyang, they must also agree on what specific steps to take when it becomes necessary to engage Pyongyang in dialogue to seek a peaceful resolution.

Taking Moon's proposal as part of that process, Japan and the United States should start coordinating their plans immediately.

--The Asahi Shimbun, July 19