After almost 30 years of trying to make apartheid a success, the South African government has admitted that, economically, the policy is a failure and probably threatens the nation's political system as a whole.

The result is a rush to replace the now discredited idea of creating theoretically independent black homelands with a new system of economic and political confederation of areas designated as "white" and "black."

Prime Minister Pieter W. Botha, in a recent speech to party supporters here, set out the broad economic outlines of what he calls his "constellation of states," which he described as a "system of regional economic cooperation between peoples who are politically organized in different ways."

The concept is a break with the apartheid ideology elaborated in the 1950s by then prime minister Hendrick Verwoerd, who envisaged that the country's black majority would eventually be citizens of politically independent and economically viable states to be created in each of 10 black tribal areas.

The myth that these rural, underdeveloped homelands could become economically self-sustaining has been dying for several years. Botha recently gave it the coup de grace, telling followers in his ruling National Party: "We have learned from hard experience that the scope for decentralization of economic activity in South Africa is limited. To ignore the high degree of economic interdependence throughout South Africa would be foolish."

The prime minister also dismissed the idea that giving more land to the black homelands, which cover only 13 percent of South Africa, would advance their economic development. "It is impossible to consolidate the geographical area of each national group in such a way that it will become economically viable on its own. And, of course, we cannot give away the whole of South Africa merely to create economically viable black states," he said.

For hard-core doubters of apartheid's economic failure, the government-established Bureau of Economic Research in Pretoria has come out with a report documenting in detail what one economist called the "embarrassing" economic failure of the homelands.

"It is evident," the report concluded, "that the development necessary to make separate development [apartheid] economically viable did not take place in the homelands. Circumstances are changing fast and there can be little doubt that the old vision must make way for a new one . . . . Change is upon us and there is a serious search under way for a new development paradigm."

While the search for a political framework for the "constellation of states" has been assigned to a 60-member appointed body that does not include blacks, the development of a new economic model is the domain of Botha's "constellation committee." Its chairman is Gerhardus De Kock, a banker who holds a Harvard doctorate in economics and spent three years in Washington on the board of the International Monetary Fund.

In an interview, De Kock explained that the constellation is to be based on the "brand new concept of economic development and cooperation in certain regions that transcend political or ethnic boundaries.

"The old idea was that the borders between [white' South Africa] and the black [homelands] would be 'hard' ones, politically, economically, in every way," De Kock said.

"The new idea is to say we are going to set up whole new development regions [where] the borders between the homeland governments and [white' South Africa] will be 'soft' for economic purposes," he explained. These growth points will be administered by regional economic authorities composed of both homeland governments and Pretoria, which will share in the revenue generated by their development, De Kock said.

Apart from economic considerations, the government's plans are on shifting sands in the political arena as well.

Right-wingers of Botha's party have publicly railed against his policies, saying that economic integration will eventually lead to political power-sharing.

Blacks have paid little attention to the "constellation," which most see as a way to prolong white domination. Some Afrikaner thinkers agree with them.

Said political scientist Andre du Pisani, "It becomes a system of control and manipulation. You neutralize black demands for access in the central government through your development aid. It's a good way to silence people."