The debate over United States policy toward South Africa -- muted since the US imposed limited economic sanctions against Pretoria last fall -- is back in full swing. On Capitol Hill, frustration with the increasingly defiant attitude of Pretoria's white-ruled government is prompting support for sterner measures to force an end to apartheid, South Africa's policy of racial segregation.
But Reagan administration officials, despite strong words against apartheid, insist that their policy of ``constructive engagement,'' meaning quiet diplomacy, remains the right one. For now, they add, there is no alternative to cooperating with Pretoria to encourage peaceful change.
``Basically we have two courses,'' a State Department official says. ``We can stay involved and use the limited leverage we have. Or we can use sanctions and exacerbate the politics of polarization.''
``They're disillusioned with the course of events, but they don't like sanctions,'' Carol Lancaster, an African affairs specialist at Georgetown University, says of the administration. ``Short of support for something like an anodyne UN resolution or a symbolic meeting with the [outlawed African National Congress], they appear to have little room to maneuver in the current situation.''
The House Foreign Affairs Committee has approved legislation that would put an immediate end to all new private investment in South Africa by American companies and impose an embargo on coal, steel, and uranium imports from South Africa. The bill would also suspend landing rights in the US for South African Airways.
``It's too late to simply talk about how much we dislike apartheid,'' says a congressional source sympathetic to new sanctions. ``We have to create a situation in which the South African government sees that a normal relationship cannot continue to exist in the United States.''
The measure is expected to pass easily in the House this week. But progress on sanctions in the Senate may be slower when it takes up the bill next month.
The influential chairman of the Senate Foreign Relations Committee, Richard G. Lugar (R) of Indiana, says he is reluctant to go along with additional sanctions.
``I know a lot of people want sanctions just to show moral outrage,'' Senator Lugar says. ``The question is whether there's anything better diplomatically or economically to move South Africa away from apartheid.'' Mr. Lugar plans hearings next month on alternatives to sanctions.
Reagan administration officials, led by Secretary of State George P. Shultz, have recently denounced apartheid in stronger terms than ever before. But despite the tough language, White House officials continue to reject sanctions as an indiscriminate instrument that would hurt blacks more than whites and produce even deeper intransigence in Pretoria.
Many experts say that only a dramatic increase in violence in South Africa would prod the administration toward a more activist policy toward apartheid.
Meanwhile, the escalating pattern of violence and repression in South Africa last week prompted public warnings from members of a Commonwealth study group. The group warned that the ``worst bloodbath since the Second World War'' could result from Pretoria's ``obstinacy and intransigence'' in refusing to dismantle the apartheid system.
Analysts say the report, together with calls for increased economic pressure on Pretoria expected from meetings of UN officials and West European foreign ministers this week in Paris, will increase pressure on the US to take a harder line toward South Africa.
Moreover, the stance taken by British Prime Minister Margaret Thatcher could influence President Reagan.
With more than $9 billion in British investment in South Africa and thousands of jobs in Britain dependent on trade with Pretoria, Mrs. Thatcher has so far been reluctant to support economic sanctions.
But as British companies quietly begin to disengage from South Africa in response to increased violence and a downward spiral in the value of the South African rand, opposition in her government to tough new economic measures could decrease. In addition, Thatcher will face strong pressure for sanctions when a special Commonwealth meeting convenes in August to consider the group's report.
Analysts say that if Britain does shift policy, this could give the Reagan administration just the excuse it needs to sponsor or accede gracefully to new sanctions.
``Given the Thatcher government's contacts with conservatives in this country, that might ease conservative opposition to sanctions,'' Carol Lancaster says.