JOHANNESBURG -- There are signs that South African President Pieter W. Botha, anxious to engage credible black leaders in a political dialogue before national elections in 1989, has embarked on a plan that will lead to freedom for African National Congress leader Nelson Mandela and other imprisoned leaders, and eventually to power-sharing talks with black radicals.

Publicly, Botha has scoffed at such speculation, belittling journalists for competing with one another in "composing wild dreams" about Mandela's release. At a provincial convention of the ruling National Party last week, he said the government would not talk with the ANC, adding, "The world cannot expect us to negotiate with people who are not prepared to make peaceful coexistence a reality."

But the president's deeds over the past six months suggest that such rhetoric is meant to placate the extreme right-wing Conservative Party, which made inroads in last May's whites-only parliamentary elections at the expense of Botha's ruling National Party.

Senior Cabinet officials admit that the thrust of the government's actions since the elections has been to lure the ANC and its supporters into power-sharing negotiations by systematically removing obstacles that black nationalists have said prevent them from participating.

Some militant black leaders, such as Anglican Archbishop Desmond Tutu, have said repeatedly that it would be unthinkable to consider joining in formal negotiations with whites as long as the legal pillars of apartheid remain in place.

Botha responded last month by giving the government's endorsement to limited reforms of the Group Areas Act, which strictly segregates communities by race. Although the reforms maintain the principle of housing segregation, they would, for the first time, permit integrated communities where residents want them.

At the same time, senior government officials, apparently with Botha's blessing, began talking about the need for "elasticity" in defining racial groups, a subtle shift that seemingly calls into question the principles of the Population Registration Act, which rigidly classifies all South Africans by race at birth.

Some moderate black leaders, such as Zulu chief Mangosuthu Gatsha Buthelezi, have said consistently that they would not consider joining in negotiations as long as Mandela and other ANC leaders remain imprisoned.

By releasing ANC stalwart Govan Mbeki last week after he had served 23 years of a life sentence for sabotage and treason, Botha appears to have begun a process that will satisfy Buthelezi's condition and bring him to the negotiating table.

In its attempt to win wider domestic and international approval of its efforts to promote a political dialogue with blacks, the government has implemented a number of piecemeal but significant reforms during the past six months.

Taken individually, they strike many antiapartheid activists as cosmetics. "Reform is aimed at implementing far-reaching changes in a society," observed Jan Steyn, executive director of the Urban Foundation. "It does not imply changes to an undesirable structure, leaving the very nature of the structure intact."

But viewed as a whole, the announced reforms over the past six months -- whatever their shortcomings -- represent perhaps the most intense period of change since the National Party came to power in 1948.

Among the changes: Following recommendations on the Group Areas Act by the advisory President's Council, Botha said it is no longer practical to separate races by residential area when some South Africans want to live in mixed-race neighborhoods. After reversing his long-standing position by declaring that renunciation of violence was no longer decisive in determining the release of security prisoners, Botha freed Mbeki, 77. The last vestiges of discriminatory "job reservation" in the mining industry were repealed. A dozen more central business districts throughout South Africa were opened for trading by all races, bringing the total of integrated business districts to 55. The government launched a nonracial Joint Executive Authority to administer Natal Province and the self-governing tribal "homeland" of KwaZulu. While it does not have lawmaking powers, the joint authority is viewed by proponents as a major step toward a single, nonracial legislature for Natal-KwaZulu. Most movie houses and drive-in theaters in South Africa were desegregated under pressure from American film distributors but with the acquiescence of the central government. The current budget increased expenditure on black education by 40 percent, while spending on white education increased only 8 percent. The government has held fast, however, to its policy of strict segregation of public schools.

As part of its policy of pacifying black townships and co-opting radical blacks who had virtually taken over the administration of the ghettos, the government began pumping millions of dollars into the upgrading of the townships' services. Botha began talking about protecting cultural, religious and language rights on a basis other than race, a basic principle of the proposed Natal-KwaZulu legislature.

In school athletics, the government has proposed a policy in which schools that do not want to compete against teams with blacks would be forced to withdraw from mixed sports events. Under existing policy, it is the teams with black members that must withdraw if any objection to racial mixing is raised. The government agreed that some black members of its proposed National Council, intended to draft a new "power sharing" constitution for South Africa, may be elected rather than appointed.

Antiapartheid activists condemned the proposal as "tokenism," and the government conceded that each of the nine elected black leaders would represent 1 million people, compared to about 20,000 for elected white members of Parliament.

But the National Council election, if approved in the next session of Parliament, would be the first time in South Africa's history that blacks were allowed to exercise an electoral franchise on the national level -- unless they boycott the election.

The National Council proposal is the heart of the government's efforts to engage credible black leaders in negotiations. So far at least, it also has been the bane of those efforts.

Constitutional Affairs Minister Chris Heunis says the government has talked with more than 170 blacks who have accepted the council in principle. For the most part, however, the dialogue has been with homeland leaders and black town council members regarded by militant blacks as collaborators with the white minority government.

Stoffel van der Merwe, the deputy minister for information and constitutional planning and the government's lead negotiator in the "talks about talks," said that the release of Mbeki and other security prisoners would deprive the ANC and leaders like Buthelezi of their reason for rejecting negotiations.

Van der Merwe, in a recent interview in the Johannesburg Sunday Star, said the government would watch closely the impact of Mbeki's release in the black townships, adding, "The future of Mandela and the others is, to some extent, in Mr. Mbeki's hands."

He might as well have said the future of black-white dialogue is in Mbeki's hands. By van der Merwe's own forecast, when Mandela and the other prisoners are freed, Buthelezi and other black leaders will soon join the talks and give them some instant legitimacy.

In retrospect, the way for such a scenario was paved as long ago as June. Van der Merwe, only a week after his appointment as Botha's point man in power-sharing talks, said then in an interview with The Washington Post that he was willing to talk with black leaders currently regarded as "radicals," providing they were not ideologically committed to a strategy of violence.

"There is nothing to be reached by drawing a lot of puppets into it, because they wouldn't be able to deliver the goods at the end of the day," van der Merwe said.

Van der Merwe indicated that even members of the outlawed ANC could be included in negotiations, and he conceded that the release of Mandela would represent a de facto legalization of the organization.

In an interview in September, van der Merwe made it clear that his views on the subject of drawing even "radicals" into negotiations were being presented with the approval of the president.

Shortly after the May elections, in which the right-wing Conservatives won 23 seats in the 178-seat white chamber of Parliament -- becoming for the first time the official opposition party -- senior government officials began signaling their motives for relaxing their policy against talking with "radical" blacks.

One Cabinet-level official explained that the leaders of the National Party, including Botha, had become fearful of going into the 1989 elections without a definable reform program to present to the white electorate.

They also felt they needed some evidence of having made progress toward bringing peace and stability to South Africa through power-sharing negotiations.

"If we go in empty-handed, we've had it," said the official, asking not to be quoted.

Another practical political explanation for the government's strategy was offered last week by John Kane-Berman, executive director of the independent South African Institute of Race Relations, in a speech to the British Industry Committee on South Africa in London.

Despite the Conservative Party gains in May, Kane-Berman said, Botha's white supporters are ready for more reform. But the president realizes that he cannot move forward on constitutional reform without credible black support, he added.

Saying that the National Party has been forced to abandon classic apartheid, Kane-Berman said that "the center of gravity of the white electorate has shifted leftward with Mr. Botha as he has abolished the industrial color bar, recognized black trade unions, repealed the Mixed Marriages Act and removed most influx control laws."

Kane-Berman, whose institute monitors race relations and apartheid laws, called the 1983 inclusion of Indians and mixed-race "Coloreds" into a tricameral Parliament Botha's "last disastrous attempt" to introduce constitutional change without black support.

Recognizing the futility of effecting constitutional change without credible black backing -- and mindful of his need to satisfy the moderate white electorate's desire for incremental reform -- Botha is trying to reach out to recognized black leaders, he said.

However, he noted, there is still a danger that Botha will become fed up with the refusal of mainstream black groups like the United Democratic Front, a coalition of 700 antiapartheid groups, to join in power-sharing negotiations and that the president will launch the National Council with the conservative black groups.

Such a forum, Kane-Berman said, would lack credibility and result in even further polarization between the government and the mainstream black leaders.