DAKAR, SENEGAL, JULY 9 -- The biggest meeting yet between South African whites, most of them dissident members of the politically dominant Afrikaner community, and black leaders of the outlawed African National Congress opened here today with both groups proclaiming partial accord.

Spokesmen said the large area of agreement dealt with the kind of nonracial democracy the sides would like to see replace South Africa's apartheid system of white-minority domination.

But key differences emerged during the closed-door sessions on strategies for achieving this, the spokesmen said. The whites questioned the ANC's commitment to guerrilla war and its alliance with the South African Communist Party, while the blacks challenged their white visitors to define a more effective way to end apartheid.

The extraordinary meeting has caught the imagination of many liberal white South Africans, who view it as an example of what they say the government of President Pieter W. Botha should do to defuse racial conflict.

The white dissidents say Botha and the right-wing parliamentary opposition have closed the door to sharing power with the black majority.

These dissidents argue that the most effective way to fend off a possible race war in South Africa is to circumvent governmental channels and seek dialogue through private contacts between white professionals and ANC leaders.

The 67 South African businessmen, professors, farmers and politicians here defied condemnation by Botha's ruling National Party and the opposition Conservatives to travel to this West African capital for four days of talks with ANC representatives in an effort to reach consensus on a vision of postapartheid South Africa.

Scores of reporters also have flocked here for the unique meeting. In South Africa, the semiofficial broadcasting service attacked the 67 whites today as "political terrorists."

Eugene Terre'Blanche, leader of the extreme right-wing Afrikaner Resistance Movement, called on the government to arrest the group when they return to South Africa on July 21 and to consider charging them with treason.

The meeting reflects a shift taking place in South African politics following a sharp swing to the right in May's whites-only election, which seemed to kill any hope that political change could be achieved through the parliamentary system.

The main thrust for change is now coming from extraparliamentary organizations, such as the one that organized this meeting -- the Institute for a Democratic Alternative for South Africa. It was founded by the former leader of the liberal opposition, Frederik van Zyl Slabbert, who quit Parliament in frustration last year.

Slabbert, an Afrikaner with high credibility among blacks, says that despite the swing to the right -- which he regards as a symptom of insecurity -- there is a growing realization among influential whites that apartheid is doomed and an alternative must be sought.

He advocates more contact across the segregated society, especially between Afrikaners and the ANC, which has been banned and silenced for 26 years. Slabbert says this will reduce white fears of black rule and sensitize black leaders to those fears.

In a speech introducing his group today, Slabbert said it consisted of individuals whose political viewpoints varied but who all rejected apartheid and were eager to explore alternatives that could lead to a nonracial democracy.

Slabbert said the group recognized there could be no solution in South Africa that did not include the ANC, which he described as "the largest and oldest movement working for liberation in South Africa."

"The significance of this meeting lies in the fact that South Africans from inside South Africa are willing in a very sincere way to examine alternatives to a brutal catastrophe that is unfolding in our country," Slabbert said.

"We are also hoping to dispel myths and prejudices about each other which are deliberately being fostered inside and outside the country," he added.

The leader of the 16-person ANC delegation, Thabo Mbeki, said the organization regards the support of white South Africans in the struggle to end apartheid as vital.

Saying he believed the whites who came here had taken the critical first step of turning away from racism, Mbeki urged them to find ways of becoming more closely involved in the struggle and thus "part of the democratic forces of our country."

The Senegalese government of President Abdou Diouf rolled out the red carpet for Slabbert's group when it arrived here last night.

The white South Africans, normally refused entry to black African states because their country is viewed as a pariah by those states, were met by top government officials and driven into the capital in a motorcade with motorcycle outriders and wailing sirens.

President Diouf opened the conference in a ceremony attended by his Cabinet and the diplomatic corps. The South Africans were entertained at an official reception at Diouf's palace tonight.