Tokyo — A political crisis of incalculable proportions looms between South Korea and Japan over the fate of South Korean dissident Kim Dae Jung. In Tokyo, Prime Minister Zenko Suzuki has taken the unprecedented step of warning that if Mr. Kim is executed, "Even if we want to continue to cooperate with South Korea, we will be unabel to do so." In a conversation with South Korea Ambassador Choi Kyung Nok, the usually mild-mannered prime minister also said that public opinion in Japan could incline toward increasing exchanges with North Korea in the event of Mr. Kim's execution.
Mr. Kim, former presidential candidate and the most prominent opponent of the present authoritarian South Korean administration, is in a prison cell awaiting the Supreme Court's ruling on his appeal against the death penalty pronounced on him by a military court Sept. 17. He was charged and found guilty of conspiring to overthrow the government.
Mr. Suzuki did not intend his remarks to be made public, but the South Korean press, which is entirely controlled by th Seoul government, has mounted a virulent cmpaign against the Suzuki comments, insisting that they constitute blatant interference in South Korea's domestic affairs.
In the United States, representatives of the incoming Reagan administration also have expressed concern over Mr. Kim's fate, and Ambassador William Gleysteen, who has been in Washington for consultations, may be returning to his post next week armed with evidence that on this issue, there is no division between President Carter and his successor.
Western diplomats in seoul are reported to be inclining toward the belief that President Chun Doo Hwan is likely to order Mr. Kim's execution when the Supreme Court hands down its ruling some time next month.
Both in Tokyo and in Washington, there has been a dispute over what tactics would best help to save Mr. Kim. Some advocated public silence and private pressure, arguing that a chorus of public protests would only inflame the nationalistic, "we'll show them" mood of the military officers who are the backbone of the Chun administration. Only quiet diplomacy, this school believes , cna succeed in gaining a last-minute pardon for Mr. Kim from President Chun.
Others maintain that Mr. Kim can be saved only by a continuation of forceful public pressure from all South Korea's major allies and economic partners -- the United States, Japan, and Western Europe.
The aim of such pressure would be to convince the South Korean authorities that Western governments have to be responsive to public opinion in their own countries, and that the execution of Mr. Kim would endanger -- if not entirely cut off -- the kind of economic cooperation under which a small, resourcepoor country like South Korea has prospered in the markets of the world.
At first, both in the United States and Japan, advocates of the "speak softly" school seem to have been in the ascendancy. But as indications have mounted that President Chum may allow the death verdict to stand, the advocates of public pressure have gained ground.
Japan, unlike the United States, has no defense ties with South Korea and cannot use pressure in this area. But Japan is Korea's closest neighbor and largest trading partner. Although Japan's ruling Liberal-Democrats have consistently supported friendly political relations and close economic ties with South Korea, the opposition Socialists have opposed such ties with equal consistency on the grounds that it is an authoritarian, undemocratic country.
While the Socialists are scarcelyn impartial in that they maintain friendly relations with communist North Korea, even among Liberal-Democrats and conservative businessmen there has been of late a noticeable swing away from South Korea and toward North Korea. This swing as yet is scarcely an avalanche, but a shock action such as the execution of Mr. Kim could change the atmosphere here overnight. In that sense political observers believe Mr. Suzuki was only putting forth a well-grounded political analysis when he spoke with the South Korean ambassador.
Korean-Japanese relations are delicate because of Japan's past history of colonial overlordship over Korea, and South Koreans often say bitterly that those Japanese who oppose the authoritarianism of the South take no account of the far more repressive communist totalitarianism of the North.
But there is widespread personal sympathy for Kim Dae Jung in Japan, partly because he was kidnapped by South Korea intelligence agents from a Tokyo hotel in 1973 and whisked back to Seoul in utter disregard of Japanese sovereignty. Whatever Seoul's orchestrated reactions against Mr. Suzuki's remarks may be, there is no question that Mr. Kim's execution would precipitate a political crisis of the first order in Japan and reopen the sensitive question of the "political settlement" of 1975 whereby the Japanese government accepted -- albeit reluctantly -- Seoul's apologies over the 1973 kidnapping incident.
Meanwhile all Kim Il Sung, the ruler of communist North Korea, has to do is to wait. Crises between South Korea and its two most important friends -- the United States and Japan -- can only the help Marshal Kim in the new image he seems to be trying to project of economic reasonableness and political detente.