AT a time when the Reagan administration has little to rejoice over in foreign policy, Africa is proving a plus. Strategically, United States prestige on the African continent is gaining at the expense of the Soviet Union.
More radical socialist states, like Guinea, are starting to think more seriously about Western alternatives to address their critical problems. The attitudes of their leaders are shifting even if those countries have not yet turned the corner in practice.
Moscow is already unhappy about intensive US diplomacy in southern Africa that is designed, in part, to limit opportunities for Soviet mischief-making.
South Africa's unprecedented nonag-gression treaty with Mozambique, its Marxist black African neighbor, is as much a coup for South Africa as it is for Washington, which served as the go-between. Washington sees the Mozambique-South Africa pact, which is intended to curb guerrilla activities, as a possible forerunner to other peaceful accommodations in Africa and believes it served as a catalyst in ending one of the logjams over Namibia (South-West Africa).
There is broad bipartisan support in Congress for efforts to rescue Africa's hard-pressed economies. An important voice in Washington summed up the situation:
''They have a perception Africa is in bad shape and is going down the tubes.''
Reagan administration offers of humanitarian assistance to Africa, where economic distress is compounded by devastating drought, meet almost no opposition in Congress. The administration requested $90 million in African food aid. Congress has pushed for $60 million on top of that.
Much of the Reagan administration's energies right now though are concentrated on the black-white divide in the southern half of the African continent. Here the administration believes it is winning a long and arduous diplomatic battle. US officials seem to be trying to curb their optimism about securing a broad peace in southern Africa. Nobody in Washington wants to appear overly confident about finally clinching a settlement on Namibia. In fact, this past weekend's talks in Zambia on this subject show how difficult such negotiations can be.
At the outset, the Reagan administration counted on a Namibian settlement as one of its first foreign policy successes. But peace signals over Namibia have been as plentiful as the flowers in spring and have withered just as quickly.
WIDESPREAD skepticism persists over whether the US really has the clout to budge South Africa or whether South Africa itself, despite protestations to the contrary, seriously intends to leave the vast, mineral-rich territory of Namibia. South Africa has never relinquished the mandate the League of Nations gave it to run the adjacent territory, even though the United Nations has asked Pretoria to give up its control.
Yet Washington is increasingly confident that South Africa now genuinely wants an honorable settlement in Namibia, provided its own security concerns can be met.
What encourages Washington is a feeling that in recent months a new chemistry is at work in the region. South Africa itself is seen to be primarily responsible for this decisive shift.
In the administration's eyes, evidence of this shift is seen in (1) South Africa's readiness to make a pact with Mozambique, (2) its willingness to withdraw its troops from southern Angola, and (3) its decision to allow the South West Africa People's Organization, the Namibian guerrilla organization, to sit down at the peace table.
Many Africa-watchers who were burned in the past by apparent South African offers to work toward peace recall only too readily subsequent retractions by South Africa in the light of ''new'' obstacles.
A cruder view is that if South Africa is posing as the promoter of peace in the region, it is only because it has succeeded in using its superior military muscle to club its weaker neighbors into submission and can now afford to appear more conciliatory.
Yet American and non-American diplomatic sources say such an oversimpli-fication of the pacification of southern Africa fails to take into account the fine tuning of American diplomatic efforts.
The impetus for a South Africa-Mozambique pact, it is noted, came from Washington, not Pretoria, the South African capital. And the benefits accruing from such a pact are not solely for the South Africans.
Within days of the agreement, a South African hotel chain came forward with a
The Mozambique-South African pact is only one piece in the larger southern Africa jigsaw puzzle devised by Chester Crocker, the peripatetic US assistant secretary of state, in his bid for a comprehensive strategy that would bring peace to all of southern Africa.
Dr. Crocker's policy, better known as ''constructive engagement'' is a series of step-by-step approaches at confidence building among suspicious and at times antagonistic states.
The policy periodically comes under sharp attack from such prominent critics as Howard Wolpe (D) of Michigan, chairman of the House Foreign Affairs Subcommittee on Africa, who thinks ''constructive engagement'' offers only carrots and no sticks to South Africa. The Reagan administration believes it operates from a more realistic standpoint. Since South Africa is the dominant force in the region, the reasoning goes, the only way it can be coaxed into releasing its tight hold over the area is to offer inducements to South Africa to persuade that government to change course.
Within that context, the South Africa-Mozambique pact fulfills the guidelines of ''constructive engagement.'' South Africa and Mozambique, under US diplomatic pressure, are urged to restrain destabilizing forces either under their control or operating from their territories.
In the absence of these acts of aggression, the countries have the opportunity to expand economic ties at a time when African economies are in a precarious state. Just as significant was Dr. Crocker's task of persuading the leadership in Mozambique that there was a Western alternative to Mozambique's reliance on the Soviet bloc, and that the Portuguese and the US could play a role as brokers. But it was made clear that this had to be done in the context of detente with South Africa, and the return of peace to Mozambique.
When that was accepted by Mozambique President Samora Machel, Dr. Crocker hurried to South Africa to add the necessary South African element to the plan.
South Africa was told that an approach of maximum toughness against Mozambique could well force it into submission, but that such a tactic increased the risks of Cuban troop involvement in Mozambique. This would compound South Africa's concerns about Cuban presence in Angola.
A South African-dictated solution also did nothing to alter the presence of African National Congress rebels on Mozambique soil. The ANC is fighting the South African government.
American capability to deliver a settlement became a function of what the Mozambicans and the South Africans were prepared to do.
After 18 months and several false starts, US diplomacy was able to glue together a Mozambique-South Africa peace pact. Washington believes the diplomatic spillover from the pact is considerable.
On the strength of that agreement, for instance, President Kenneth Kaunda of Zambia felt emboldened to call in mid-February for a tripartite meeting of Angolans, South Africans, and Americans in his nation's capital, Lusaka. The object: to provide a mechanism to jointly monitor a South African troop withdrawal from southern Angola.
Talks in Lusaka this past weekend included SWAPO leader Sam Nujoma, a coalition of internal Namibian parties, and a high-level South African delegation. However, at time of writing, the talks appeared in danger of collapse.
South African Prime Minister Pieter Botha's visit to London next month, at the invitation of Prime Minister Margaret Thatcher, is to some extent a reward for South Africa's more outward-looking foreign policy in southern Africa.
One link between the Mozambique-South Africa pact and the Angolan-South African monitoring commission was the US ability to lean on the Mozambican leadership to use its influence on the Angolans.
The rationale was that since the two countries had similar political ideologies, spoke the same language (they are both former Portuguese territories), and gained independence under the same revolutionary mystique, Mozambique was best able to persuade Angola to use the good offices of the US to deal with South Africa.
The burden on Mozambique was to assure the Angolans that if they could see the US as an honest broker, South Africa might also be forthcoming on the Namibian front.
One of Dr. Crocker's inner circle, Frank Wisner, former US ambassador to Zambia, was dispatched to Cape Verde Islands last Jan. 20 to sound out the Angolans. They came aboard. The next day Crocker rushed to South Africa with Angola's agreement. South Africa agreed and announced on Jan. 27 that it wanted a Namibia settlement and would begin to disengage its trops from Angola.
The terms under which South Africa accepted a phased withdrawal from Angola were that the US would act as a liaison between the two countries and that no parties to the Namibian dispute would take advantage of the South African withdrawal. A process of South African disengagement followed and is still going on.
The next stage is not formulated quite so neatly. But the hope is that once South Africa fulfills its part of the bargain and withdraws all troops from Angola, Angola could then proceed with a reciprocal arrangement. Angola would then have a face-saving formula that would allow it to send Cuba's troops home because the pretext for the Cuban presence in Angola - the South African military presence - would no longer be valid.
As the Reagan administration sees it, the removal of all foreign forces would pave the way for implementation of Security Council Resolution 435, which would result in full independence for Namibia.
If the diplomatic pieces fall into place, Angola, freed of Cuban presence, would receive diplomatic recognition from the US and, presumably, US aid to develop its natural wealth. Angola, although one of Africa's poorest countries, is rich in oil and minerals. South Africa's standing also would rise on its relinquishing of Namibia.
Dr. Crocker has carefully apprised front-line state leaders Machel of Mozambique, Kaunda of Zambia, and Julius Nyerere of Tanzania of developments. His strategy encountered no opposition.
Although the front-line states have subsequently met to find ways of responding to ''constructive engagement,'' their criticism is largely muted, and there is a readiness to concede privately that the American strategy is at the moment the only diplomatic ball game.
''If the Angolans are willing to go along, it is not for us to say they shouldn't,'' a front-line state's ambassador state said.
But the constructive engagement policy leaves some of the principal parties to the overall black-white dispute in limbo. The policy is directed toward dialogue among states, therefore it has restricted the role of such rebel groups as the ANC.
Individual black states, not South Africa, bear the onus for ending destabilization moves under the plan, for it is the African states that until now provided rebels with refuge.
An ANC official complains bitterly that the African states were too weak to resist South African pressure.
A criticism of constructive engagement is that the policy presumes that improvement for blacks in South Africa can come about only through reforms by Pretoria.
SWAPO's unhappiness with constructive engagement was reflected in the recent killing of two senior US officials in Namibia. Constructive engagement rules out the option of military solutions.
Washington's answer to SWAPO is that a negotiated settlement can only put the rebels in a stronger position since, militarily, they have been badly beaten by South Africa and are farther from the South African border.
Any settlement in Namibia necessarily raises the question of what role Jonas Savimbi, leader of the rebel Angolan organization UNITA, would play in Angola and to what extent South Africa will exert pressure to enhance his position there. South Africa apparently had no qualms about withholding support for rebels it has supported in Mozambique, but throwing Savimbi overboard is not considered a South African option.
The US is trying to convince South Africa and the black states that they have a common goal in promoting regional stability and respect for the sanctity for borders. If this works, the Soviet Union stands to lose the most.