The Japanese government is trying to prevent a spreading antinuclear movement at home from undermining Tokyo's close cooperation with Washington.
The biggest concern is with the growing number of local governments, from prefectural assemblies to village councils, now passing various kinds of resolutions gainst nuclear arms.
Prime Minister Zenko Suzuki, who will attend the second special session of the United Nations General Assembly on Disarmament (June 7 to July 9), publicly voiced concern recently. He said that ''extra care should be taken to see to it that these moves will not be tied up with any anti-American campaigns.''
Government officials insist that Japan, the only country to have suffered an atomic attack, intends to remain in the vanguard of the international antinuclear struggle.
At the same time, Mr. Suzuki expresses understanding of the Reagan administration's determination to narrow the gap in the nuclear balance, which in the administration's view, now favors the Soviet Union.
Thus, he is torn between loyalty to an ally and a need to maintain a commitment to the disarmament cause.
Recent newspaper surveys indicate at least 860 of the nation's 3,302 local governments, including three-fourths of the prefectural assemblies, have already passed some form of antinuclear resolution.
Suzuki argues that the resolutions are meaningless, as the government and the ruling Liberal Democratic Party are firmly adhering to their ''three nonnuclear principles.'' These are not to manufacture, possess, or permit the introduction onto Japanese soil of nuclear weapons.
But this has not discouraged the sudden emergence of an unprecedented grass-roots movement that seeks to involve a good part of Japanese in advance of the UN Disarmament Conference.
A series of antinuclear rallies is scheduled in the next few weeks in several parts of the country, including Hiroshima and Nagasaki, the two cities destroyed by American atomic bombs in 1945.
They are sponsored by the ''conference for the promotion of a public movement for the total abolition of nuclear weapons,'' which is seeking 30 million signatures on a petition to the UN meeting.
The movement is headed by 78-year-old Yoshio Nakano. This highly respected left-wing scholar and writer is one of the nation's best known authorities on English literature and also a translator of Shakespearean plays and other classical works. He has long been an activist in the peace and human rights movements, as well as a leader in the Japan-Soviet Exchange Association.
Nakano explains the petition is designed to (1) inform the world of the devastation and suffering caused by nuclear bombing, (2) achieve an international agreement outlawing use of nuclear weapons, (3) expand nuclear-free zones around the world, and (4) establish a clear timetable for total disarmament.
Another important figure in the movement, composer Koji Nakano (no relation), says: ''The government says antinuclear movements are anti-American. But we are opposing the whole concept of nuclear arms regardless of which nation possesses them.''
Politicians are involved in the movement, he says, but parties as such have been deliberately given a subordinate rule to avoid any accusations of factional political bias.
Those involved in the new grass-roots movement say that, despite its unique position, Japan has lagged behind Western Europe and the US in opposing the nuclear arms race.
But after a lengthy decline, the Japanese antinuclear movement has revived, reflecting several influences: encouragement from the resurgent antinuclear movement in Western Europe; concern over the nuclear expansion policies of the Reagan administration; suspicion about Japanese government intentions.
There has also been skepticism over the government's commitment to the three nonnuclear principles, especially since the revelations by Dr. Edwin Reischauer suggesting that, as a matter of course - and with Tokyo government compliance - American nuclear weapons have been brought into Japan on and off for many years.
Some commentators, however, suspect it may be a case of the Japanese indulging in their well-known trait of seizing on something ''fashionable'' for the moment, and it is really too early to say that a genuine deep-seated national antinuclear movement has finally emerged.
The campaign was launched by a mass rally in Hiroshima. Its numbers were estimated at 200,000 by the organizers and 95,000 by police. As many as 300,000 are expected at a Tokyo rally in mid-May. Organizers hope to arrange ''peace trains'' to bring supporters from all parts of the country.
To bring home the meaning of atomic warfare, survivors of the twin 1945 bombings are being encouraged to speak out.
A book to be published in May recounts the experiences of the ''atomic bomb widows' village.'' This is a small community about 10 kilometers from central Hiroshima in which 75 women lost their husbands in the bombing 37 years ago. A film obtained from the US will be screened around the nation of hitherto unseen footage of the bombing aftermath.