THE REAGAN ADMINISTRATION'S posture toward the Republic of South Africa should surprise no one who has watched the growing preoccupation of American politicians with protecting access to natural resources and preserving vital economic arrangements. The Iranian revolution and hostage crisis, along with the Soviet invasion of Afghanistan, brought home the message that only blind faith could guarantee a steady supply of oil from the Middle East. While a re-election campaign motivated President Jimmy Carter's plans for a rapid deployment force and promises to defend the straits of Hormuz from outside invasion, there has been no equivocation in his successor's intentions. President Reagan and Secretary of State Alexander Haig have made explicit the administration's commitment to protect vital areas from the threat of Soviet aggrandizement and other efforts to destabilize regimes that otherwise serve U.S. interests.

The most publicised example of this policy in action has been the administration's attempt to negotiate a sale of American-built AWACS surveillance planes with the Saudi Arabian regime, but the government's move toward closer relations with South Africa also fits into the scheme. Politically embracing the white-dominated regime is understandably an alluring proposition for the administration. The country's near-monopolies on the world's gold, diamonds and aluminum make trade with South Africa an essential resource value for the economies of the United States as well as other nations. Moreover, South Africa's domination of the peninsular tip of the continent effectively counters Soviet and Cuban presence in other parts of Southern Africa.

Of course, backing South Africa whole-heartedly is problematical, not to mention immoral. Its apartheid policy, euphemistically spoken of as "separate development," has alienated South Africa from nations around the world since the policy was enacted more than 30 years ago. U.S. policy has been one of officially-stenciled indignation since the Kennedy Administration decided to ban arms sales in the early 1960s. Most recently, under the Carter administration, a squadron of humanrights-oriented officials enforced tight restrictions on the flow of technology to South Africa and demanded better treatment for the country's majority Black population.

Apparently, the recent shift to the right in American perspectives on global politics has convinced the Reagan administration that it can improve relations with the P.W. Botha regime in South Africa without alienating too many liberals or Blacks in this country. The administration has set in motion a new policy of "constructive engagement" with South Africa that government officials say will benefit both nations, while bettering conditions for the racial majority of South Africa. "We can cooperate with a society undergoing constructive change," Chester A. Crocker, Assistant Secretary of State for African Affairs, has said. From this watershed in U.S.-South African relations would flow, Crocker says, a new spirit cooperation in all sorts of strategic and economic concerns, scientific--especially nuclear interchange--and perhaps some military agreements.

BUT THE ADMINISTRATION'S policy shift has not been without its critics, U.N. ambassador Jeane Kirkpatrick's consultation last March with high-level South African intelligence officials aroused fears that "constructive engagement" would involve Americans in the South African regime's repression of Blacks. A series if unexplained but highly-official diplomatic shuttles between Pretoria and Washington, along with voices of outcry from Black African capitals, added to the sense of confusion. More recently, a Reagan Administration's effort to back South Africa officially in certain areas has become clear, most prominently its pledge to veto any resolution in the U.N. security council explicitly condemning Pretoria for its invasion of Angolan soil. In addition, several minor but concrete concessions have been made by the U.S. to the South Africans, most notably a plan to increase the number of military attaches in each country.

"Constructive engagement" relies on several premises. The first, that no internal resistance movement seriously threatens the stability of the South African regime, is probably a fair assessment. No ideology of mass violence has ever captured the spirit of the Black South Africans; uprisings such as the Soweto riots of 1976 have generally been tragic, isolated incidents. Journalists in that country also report that resistance efforts such as the African National Congress have lost much of their past potency. Only time can prove the merit of the judgment, but armed insurrection in the near future seems unlikely.

The Reagan administration's hopes for constructive cooperation with the South African government rest partly on the country's promise of future stability, but also on the Botha regime's actual commitment to reform of South Africa's apartheid system. It is upon this premise that Reagan's friendly posture toward the divided nation fails. Prime Minister Botha has presented his leadership as an appeal to serious reform of the laws and customs that have restricted Black opportunities and mobility for decades, but changes under his leadership have proven largely insignificant, more a paean to his political rhetoric than an indication of substantive change. His regime has accomplished reform, of course, but the reform was simply the natural outgrowth of the progressive posture much of the nation took after the 1976 outburst in Soweto. The five years since then have shown that the system of white supremacy could survive intact without radical change.

The only significant reforms--legalization of Black labor unions and efforts to educate a middle class of Blacks-stem directly from the shortage of skilled labor facing South African industrialists. Some doors have opened for Blacks, but segregated washrooms, restaurants and hospitals predominate. And a public uproar was stirred recently a Johannesburgh high school fielded two black youths on its rugby team, ultimately leading to the removal of both athletes.

United States efforts to work with the Botha regime toward any liberal reform in South Africa will have to face an increasingly reactionary white population there. Last month's nationwide election showed a large split in the ranks of Botha's controlling national party with only a small per cent defecting for the Progressive, and almost one third of all Afrikaaners supporting the Herligte National Party, a reactionary splinter group willing to allow no concessions for the nation's Blacks. The whites, perhaps with due cause, fear that their survival as Afrikaaners is at stake, and claim any concerted effort at reform can only lead to their entire system unravelling.

THE CONSERVATIVE BACKLASH leaves questions about more than the morality of the Reagan administration's dealings with the South African government. Other questions abound, especially about the possibility of cooperation with a country growing increasingly intransigent.

South Africa has little to gain from cooperation with the United States besides the degree of legitimacy that American backing gives in international circles. Pretoria evidently found the new Reagan administration's support helpful last January when it reneged in its agreement to submit the territory to U.N.-monitored elections. U.S. backing of its puppet government in Namibia bolstered the Botha regime's smug refusal to recognize the Soviet-backed Southwest Africa People's Organization as the best representative for the peoples of Southwest Africa. Reagan and the United States can feel justified in demanding the guarantee of minority rights in Namibia. But past experience indicates that South African foot-dragging serves only to protect the interests of the area's Afrikaaner mining population.

In short, the United States has little influence on either the domestic or foreign policies of the South African government. Alienated from normal relations with the rest of the world for long enough, the South Africans know little will change with good behavior. Ties with the Reagan administration can only unite the two countries in the perceptions of the rest of the world's nations, especially Black African countries that will refuse to understand how minimal U.S. leverage actually is. With little change among the South Africans, the Reagan administration will have to ask if the price is worth the benefits of "constructive engagement."