More than 40 District ministers and community workers met last week at a prayer breakfast hosted by Del. Walter E. Fauntroy to plan a grass-roots campaign against the South African government's apartheid policies.

The breakfast was sponsored by the D.C. support group of TransAfrica, a national lobby for black Africa and the Caribbean. It was part of an effort to heighten awareness here of what the group calls an international movement against South Africa's system of racial discrimination by which its 4 million whites maintain economic and political domination over its 20 million black citizens.

"We want to organize a microcosm in the Washington area of the TransAfrica lobby," Fauntroy told the group gathered at New Bethel Baptist Church, Ninth and S streets NW, where he is pastor. "Our purpose is to develop a black constituency in America for Africa."

George Dalley, a member of the Civil Aeronautics Board who heads the local TransAfrica group's planning committee, said its aim is to enlist the help of the District's black churches. Specifically, churches were asked to buy and display signs demanding freedom and equality for South African blacks. The signs, which cost $200 each, are being sold to raise funds for TransAfrica's lobbying efforts.

Fauntroy stressed the need for financial support generated from the black churches. He also asked each church to buy a $1,000 table at an annual TransAfrica fund-raising banquet scheduled here for next June. Although the organization is supported partly by foundation grants, the yearly dinner is its chief source of revenue.

Three District churches already display the 4-by-4-foot signs reading "Let's End U.S. Support for South Africa." They are Shiloh Baptist Church, 1500 Ninth St. NW; Calvary United Methodist Church, 1459 Columbia Rd. NW, and St. Paul & Augustine Roman Catholic Church, 15th and V streets NW. A fourth sign, outside All Souls' Church at 16th and Harvard streets NW, was destroyed by vandals early this year.

An earlier version of the sign, saying "Free South African Blacks," stands in front of St. Timothy's Episcopal Church, 3601 Alabama Ave. SE.

Other churches, including Metropolitan A.M.E., 15th and M streets NW, have placed their own anti-apartheid signs on external church billboards in solidarity with the movement, but have chosen not to make the $200 contribution, according Dr. James Davis, planning committee secretary..

Some churches are financially unable to purchase the signs, according to the Rev. Fred Harrison, pastor of St. Paul A.M.E. Church, 4901 14th St. NW, who lived in South Africa for three months in 1972. His church declined to purchase a sign earlier this year, Harrison said, because at the time "we didn't see the value of a $200 sign," he said. Harrison suggested that a fund-raiser or banquet be held to raise money to purchase signs for every church in the District.

"We want to see a sign on every major thoroughfare in and out of this city so that lawmakers will know the black community is outraged at the current policy of South Africa," said Davis.

The 18-month-old D.C. Support Group is among the largest of the 13 local TransAfrica support groups nationwide. It is governed by an 11-member planning cadre, which has a mailing list of 150 with approximately 50 dues-paying members, according to Davis.

The support group is also charged with increasing participation by area churches in local demonstrations, according to Davis.

"If we hear that (South African Premier Pieter) Botha is coming, we'd like to mobilize people to 'greet' Botha," he said, noting that it should be easy to do through the already established social action committees in most churches.

In addition to the sign campaign, the District group is participating in TransAfrica's Action Alert Network, a series of letter-writing campaigns directed to congressmen in the 13 areas that have support groups.

Ann Holloway, staff director of the House Foreign Affairs Committee's subcommittee on Africa, said a local support group should be effective in educating the public through hearings, study groups and letter-writing campaigns to key members of Congress. She said the increased grass-roots participation would broaden the power base of TransAfrica and thereby give more credence to the group's testimony on Capitol Hill.

Holloway, who was U.S. ambassador to Mali from 1979 to 1981, said TransAfrica's efforts have helped produce several pieces of proposed legislation, among them a prohibition of U.S. nuclear-related dealings with South Africa, prohibition of new U.S. private bank investments and a freeze on private bank loans in South Africa, prohibition of the sale of South African Krugerrands in the United States and mandatory fair employment procedures by U.S. companies operating in South Africa.

Holloway told the ministerial group that involvement in the struggle for the rights of South African blacks is the "unfinished business" of American blacks. She urged the churches to provide moral support for the movement by raising the consciousness of the community.

Harrison acknowledged it might be difficult to persuade congregations that international involvement is a priority when there are so many economic and social problems in their own community.

"But exposure is the key," he said, "exposure to meetings like these, where the people can put a face on problems like apartheid."