Congress considers boosting sanctions against South Africa. The Reagan administration and Congress are facing off over South Africa again. Legislators want more sanctions. The White House says quiet diplomacy continues to be the best policy.

The debate is again on in Washington: How can the United States most effectively contribute to the elimination of apartheid in South Africa? The House of Representatives today begins initial hearings on the issue, which come in the wake of last month's Senate hearings.

A year ago the Congress overrode President Reagan's veto and imposed limited economic sanctions on South Africa. The goal was progress toward ending the apartheid system of racial segregation and, in the short term, stopping abuses of civil and political rights in South Africa and South Africa's destabilization of its neighbors.

Last month, Mr. Reagan told Congress something everyone agreed on - the sanctions had had little effect and the situation in and around South Africa had worsened. The President also declined to recommend further sanctions, as the law suggested he should. Instead, he called for a period of ``active and creative diplomacy'' focusing on bringing the peoples of South Africa together for meaningful negotiations.

Congressional activists from both parties are very critical, saying this continues what they call the administration's ``ineffective'' policy, once known as ``constructive engagement.'' They criticize the administration for the way it carried out sanctions, which they say ended up giving South Africa several trade loopholes. And, they add, the administration failed to apply the provision of the law asking it to organize an international conference of Western countries aimed at agreeing on similar sanctions.

A number of bills have been introduced in Congress, including ones calling for comprehensive US economic sanctions sponsored by Sen. Alan Cranston (D) of California and Rep. Ron Dellums (D) of California.

Current prospects for new legislation are unclear. Sanctions supporters are trying to build momentum for some sort of reinforcement of existing sanctions, while the administration explains its rationale for holding off. At base, the two sides remain divided as to the best strategy for changing apartheid.

The administration says sanctions have a role, but it is important to be able to talk to both sides and encourage dialogue.

Congressional critics say sanctions are the only way to bring home to the South African regime that it is internationally isolated and must respond to the demands of the country's black majority.

``Sure, we're all impatient to overturn this terrible system,'' one well-placed official specialist says, ``but we can't solve the problem for the South Africans.'' The US can continue to pressure and persuade, but cutting itself off from both sides with sanctions ``is not a viable alternative,'' he says.

Administration officials say the US does not have support for a sanctions effort among major Western countries, thus South Africa will likely be able to bust any US trade sanctions.

If by chance a reasonably effective sanctions regime was imposed, the white community would hunker down and be even more repressive, they argue.

``White South Africans will be much more resistant to change if their survival instincts take over,'' one US diplomat with long service in the area says. ``Look how long white Rhodesia [now black Zimbabwe] held out once it was forced to close ranks by international sanctions.'' He says one already sees this in South Africa's white right-wing backlash and says this shows why channels must be kept open.

Thus, the best policy, officials argue, is to be present to aid blacks, to encourage reformist whites, and to retain leverage of inducements and sanctions on South African government policy.

Chester Crocker, the assistant secretary of state for Africa, argues that rather than sanctions, Congress should vote more aid for black ``empowerment'' and training projects that the administration has sought, as well as the full aid requested to bolster neighboring countries so they can better resist South Africa's pressures.

He also says the US should be more active in sharing its vision of what a future democratic South Africa should be like, and should actively work to bring parties together to help them find common ground.

Congressional critics, such as Rep. Mickey Leland (D) of Texas, say the administration's attempt to follow such a policy has failed and the situation has worsened. More effective and comprehensive sanctions are needed, Mr. Leland argues.

The administration's record of carrying out limited sanctions, however, helped spur significant ferment in the white South African community, says Rep. Howard Wolpe (D) of Michigan.

Mr. Wolpe, who is chairman of the House subcommittee on Africa, says sanctions are not a cure all, but they will cut the psychological links between the Afrikaners and the outside and make clear the long-term costs of the current South African system.

The critics say most black South African leaders call for international sanctions as an aid to their struggle. This includes Anglican archbishop Desmond Tutu, who won the 1984 Nobel Peace Prize, and major black union federations, whose workers have voted pro-sanctions resolutions, despite possible job losses resulting from sanctions.

James Motlatsi, president of the South Africa's National Union of Mineworkers, explains his union's call for international sanctions by saying that when workers regularly die in work accidents and are fired for legal strikes, when their children are shot by police, when their families suffer malnutrition in the homelands far from them, possible job loss as part of changing the regime is worth the risk.

Sanctions remain a hope for peaceful change, he says, because they aim to shock the government into serious negotiations.

Congressional and administration sources do see the momentum for imposing stronger sanctions in this session.

However, congressional irritation over the administration's failure to convoke an international gathering to consider sanctions and its perceived poor implementation of other provisions could result in congressional action reinforcing existing legislation. For the longer term, Leland, who was chairman of the Congressional Black Caucus when the Comprehensive Anti-Apartheid Act was passed last year, says sanctions advocates plan to make the issue important in next year's congressional elections. South Africa is the No. 1 foreign policy issue for US blacks, he says, and the failed nomination of Judge Robert Bork to the US Supreme Court shows the network of black organizations can have a powerful impact.