Black nations of Southern Africa are prepared to suffer the consequences to their own economies of western sanctions against South Africa because "there is no other alternative," according to a spokesman for a nine-state regional development grouping.

"Sanctions are a road not to a peaceful change but a less violent change," said Simba Makoni, executive secretary of the Southern African Development Coordination Conference, in an interview here last week.

"Yes, there is going to be suffering, but it's inevitable," said Makoni, adding that South Africa's black neighbors were "already suffering a lot."

"There can no longer be talk of a peaceful solution," he said.

According to conference calculations, the cost of South African "aggression" and "destabilization" against its neighbors since 1980 has been $10 billion, including $1.6 billion in direct war damages.

Makoni indicated that black nations of Southern Africa had few illusions about obtaining any additional aid from Washington or London to offset the effects of sanctions against South Africa, though they have been seeking help to cushion them against the effects.

"The general indication we get is that the United States will not be willing to assist us," he remarked. "We have that message loud and clear."

Makoni said that despite the bleak prospects of additional western aid, his group had concluded that sanctions were "an effective force for change" and "inevitable."

He defended such curbs against critics who argued that, in the case of white-ruled Rhodesia (now Zimbabwe), sanctions had failed, saying that if applied "genuinely and honestly" they could be effective. But he seemed to have doubts whether the United States, Britain or West Germany had the "mentality" or "psychology" to make them work.

Makoni belittled South African threats to retaliate against its African neighbors for international sanctions. A recent report said the government there was preparing "contingency plans" to send foreign black workers home.

South Africa estimates that there are up to 1.5 million such workers in the republic. But Makoni said many of these were residents of South Africa's own "homelands" and that "not more than 400,000" were citizens of neighboring nations.

He said the South African economy was also dependent on its neighbors for skilled mine labor and markets, adding that "it's not entirely a one-way trade."