Condemned by rightist Dutch Reformed clergy and spurned by activist leftist Christians, 5,000 black and white South Africans are meeting here this week in one of the largest multiracial ecumenical gatherings ever held in this country.

While the participants are enthusiastic about gains they expect to achieve through their once-improbable interracial contacts, the sensitivity of their gathering has resulted in some rigid self-constraints.

No political statements are planned, and no frontal challenge on South Africa's official policy of apartheid is likely.

Instead, they have set as their modest goal the slowing of the polarization between black and white Christians in South Africa, as blacks increasingly see no benefits for them in the gospel and view their fellow Christians as little different from those who espouse the injustices of apartheid.

A middle-aged white Afrikaner, brought up on the racial segregationist doctrine of apartheid, animatedly told a friend this week how, in greeting another participant at the conference, he had "hugged a black woman for the first time."

A colored (the government designation for mixed race) minister told of a colored woman at the conference going to a dormitory to spend the night after turning down an offer to sleep at the home of a white family. When he asked her why she had done this, he said, she explained that she had been afraid because "what would we talk about, brother?""

These are two examples of the personal confrontations occurring in the conference, one of the few places where large numbers of South Africans of all races are gathering specifically to address racial questions.

The 10-day conference, called "in light of the serious situation" of racial polarization, according to its organizers, is sponsored by the South African Christian Leadership Assembly.

Its multiracial organizers, who acted as individuals and not as representatives of their churches, say the main thrust is to improve personal relationships, not to take political stands.

This character of the conference helps explain two things.

First, it is the reason why activist Christian groups, who are pushing for organized churches to be more vociferous in opposing government policy, and urban balck youths, many of whom regard the church as a hinderance in their struggle for freedom, charge that the assembly is useless unless it takes a political stand on the inequalities of apartheid. Second, the limited goals help explain how such a conference was allowed to take place despite the protests of rightist clergy in the government-suppporting Dutch Reformed Church. A prominent Dutch Reformed minister, Koot Vorster, brother of former prime minister John Vorster, charged that the ecumenical gathering was a "front" for liberals and communists to destroy the white Afrikaner.

The self-restraints mirror the restrictions imposed on the white South African Christian establishment by the government and police, which few clergy are ready to challenge. When white church leaders do stick their necks out to identify with black aspirations, they are quickly stifled.

This South African Christian Leadership Assembly had its origins in a 1976 ecumenical conference in Nairobi, Kenya: the Pan African Christian Leadership Assembly. At that conference, a delegation of South Africans, after initial hostility, was accepted into the group.

Because of that experience, South African Christian leaders, distressed at developments here, began planning their own assembly.

They sought financial aid from churches here, in Western Europe and the United States.

They sought no assistance from the World Council of Churches because of that group's controversial actions in giving aid to liberation movements of southern Africa.

"If we got aid from the WCC we never would have been allowed to hold this conference," said Willem Saayman, an organizer of the current conference.

In a keynote speech, an Afrikaner Dutch Reformed minister and professor of theology, David Bosch, was applauded when he called for an activist role for the church, but not one that would thrust the church into a completely secular arena. He added that by avoiding social problems, "We then offer society on a platter to Marxism."

"The church can never acquiesce in the reality of widespread unemployment, bad housing, an unjust wage system, lack of freedom, disruption of family life, lack of participation in decision-making processes...systematic and revolutionary violence," Bosch told his audience, which was about 60 percent white and 40 percent black.

Despite its limitations, the conference attracted a number of outspoken black churchmen, including the general secretary of the South African Council of Churches, Desmond Tutu; Methodist minister Alliot Mgojo and Lutheran Bishop Manas Buthelezi.

These men, dissatisfied with the complacency of many white Christians, pressed for a more activist church.

Buthelezi said that the "obvious stand for the church to take" is that of calling blacks and whites to the conference table "for the purpose of negotiating a lasting political settlement. Otherwise the church will be accused of condoning white resort to violence while condemning blacks if they resort to exactly the same methods."

So far, no Christian church in South Africa has, as an organization, demanded such a political conference.

For now, they are devoting themselves to improving the conditions under which blacks live and to reconciling Christians - black and whites - on a personal level.

But this, it appeared here this week, may not be enough to stem the drift toward polarization.

At the close of one multiracial discussion, a colored minister prayed that God would help " those whites who are struggling to overcome their prejudices" and would give patience to "those of our people who are beginning to hate whites."