Archbishop James A. Hickey yesterday called for a bilateral freeze on nuclear weapons and formally launched a campaign to mobilize the 400,000 Roman Catholics of the Washington archdiocese to study the "moral dimensions" of nuclear warfare.

The campaign, outlined in a 3,000-word pastoral letter to be issued today and in a special eight-page supplement of this week's archdiocesan newspaper, will be one of the most intensive efforts ever focused on a social issue by the archdiocese.

In discussing the pastoral letter, his first as head of the Washington archdiocese, Hickey yesterday emphasized the religious questions raised by nuclear warfare. "I see it not just in military terms or political terms, but in terms of survival," he said. "We're talking about something that has the possibility of serious harm to God's creation."

Hickey, who has taken an increasingly activist stance on national and international problems since coming here nearly two years ago, is establishing a task force to prepare what he described as "balanced and useful materials" for study of nuclear warfare and to stimulate such study activities in local parishes.

He also plans an archdiocesan Conference on Nuclear Weapons and the Arms Race, to be held next fall for parish leaders. Clergy of the archdiocese were briefed yesterday at a a day-long conference on the topic.

He declined yesterday to speculate about the possibility of mobilizing Catholics into a political action force as a result of the study campaign.

Hickey, his two auxiliary bishops and top administrative staff members already have completed a three-day seminar on nuclear issues. Seminar participants included theologians, government officials, doctors and political scientists, ranging from former CIA director William Colby to antinuclear activist Roger Molander.

In his endorsement of a nuclear freeze, Hickey joins a growing number of Catholic bishops who have spoken out individually against nuclear weapons, but he is believed to be the first to establish such a study program involving all members of a diocese.

The National Conference of Catholic Bishops has been working for two years on a formal position paper on nuclear warfare. It is expected to be presented at its meeting in November.

Hickey linked his diocesan-wide study program to that upcoming report. "I am concerned to have our Catholic people thinking about these issues," he said. "I felt I could make a contribution to the hierarchy's November pastoral with a sounding of how my people felt, and also . . . the people would be in better position to hear how the bishops felt if they'd been doing a lot of thinking."

In his pastoral letter, Hickey stresses that every Catholic "is called to be a peacemaker; this is not an optional commitment."

In announcing his support for "a mutual and verifiable nuclear weapons freeze tied to future reductions in nuclear arms," Hickey writes, "I ask you to reflect with me on the growing risks of nuclear war--the growth in the numbers, power and sophistication of nuclear weapons; the discussion of winning or surviving nuclear war; suggestions of demonstration nuclear explosions and how to regain nuclear superiority. I ask you to reflect on what legitimate defense and national security mean in a nuclear age."

Hickey said he addressed the question "not as a politician or scientist, not to join some ideological bandwagon, but to meet my responsibilities as a teacher and pastor within the Catholic community, which has a long-standing tradition of concern for the moral dimensions of warfare and conflict.

"Issues involving fundamental matters of life and death cannot be settled merely with political or technical arguments, although political skill and technical competence are important," he said. "Too often the discussion of national nuclear policy has neglected ethical concerns and excluded the broad public discussion required on matters of such profound significance."

The supplement published in the archdiocesan paper, the Catholic Standard, includes, in addition to the text of the pastoral, statements of popes and other Catholic leaders on nuclear warfare, plus a map and graphic description of the devastation to be expected from one nuclear hit on the White House.