The United States and its allies should accelerate their drive to build up stockpiles of strategic minerals and ease dependence on South Africa for certain critical raw materials.
That's one recommendation of a staff report from the Senate Foreign Relations Committee.
At the same time, the report urges, the US should continue to pursue whatever ''symbolic'' actions it can to pressure the white-ruled southern African nation to loosen its stringent policies of racial segregation.
But imposing economic sanctions, or discouraging business investment in the country, will probably do more harm than good in trying to bring about change, the study warns.
The congressional study on the depth of US mineral dependence on South Africa and what can be done to reduce it comes at a time of increasing concern about American vulnerability to the loss of critical raw materials in general.
Of some 36 minerals the US considers of strategic importance, more than half are now imported. The US depends heavily on South Africa for at least four of these: chrome, manganese, vanadium, and platinum. The minerals are essential for oil refining and making specialty steels, and they are used in aerospace and other defense-related industries.
For the past two years the Reagan administration has been trumpeting the need for the US to stuff more minerals away in its critical-material vault. It has accused the Soviet Union of engaging in a ''resource war'' with the US, particularly in mineral-rich southern Africa.
The new congressional study, however, sees Soviet meddling as unlikely to cause a cutoff of mineral supplies from South Africa. Instead, internal strife - such as labor unrest - is seen as the most likely cause of any disruption in the supply of materials. To protect against interruptions in the flow of minerals, the report suggests that the US should:
* Expand ''modestly'' its stockpile of strategic minerals, bringing levels up to capacity. Although the US stockpile does include the four minerals supplied by South Africa, some of the stocks are well below target levels.
* Encourage joint-stockpile planning with members of the Organization for Economic Cooperation and Development. Some US allies have balked at the idea of a mineral stockpile. The report suggests that the US should consider using export controls to persuade those countries reluctant to take part in the planning.
* Explore federal tax incentives and subsidies that would encourage companies to keep mothballed processing plants in working condition. Besides importing key minerals, the US has become more dependent on South Africa to process some of them, because various US plants have deteriorated.
* Search for ways to reduce civilian consumption of vital minerals during times of shortage. For instance, the report says, legislation could be enacted that would temporarily suspend federal emmission-control standards on new cars if mineral supplies were cut off. Catalytic converters account for more than half the annual US consumption of platinum.
The study, however, doesn't favor the idea of using federal subsidies to spur more private-sector development of strategic minerals in foreign countries. It says federal dollars could be better spent building up existing stockpiles.
In the long run, the study says the US should continue to try to nudge South Africa away from its system of apartheid (racial separation), and thus try to prevent future strife in the country. There should be continued backing for worker training and educational programs for blacks.
The report also suggests the US should remain ''distant'' from the South African regime. But it says applying economic pressure against the country - such as through an embargo on mineral exports or a cutoff of foreign investment - would do little good, because Western nations' dependence on South Africa for critical materials is greater than South Africa's dependence on them for foreign exchange.