"Opponents of Apartheid Arrested in South Africa" read the headline. It happened to run the other day, but it could have run at almost any time in the last five yars, or earlier, and it is likely to run countless times in years to come. For the condition to which it alludes -- white minority rule and resistance to it by blacks and some others -- defines reality in South Africa. Apartheid has proved to be hardy and, in its fundamentals, relatively impervious to reform. Something similar might be said of resistance: hardy and, in its fundamentals, relatively impervious to repression. The stage for a continuing confrontation is set.

In this country, the Carter administration quickened the sense that morally and politically the United States had reason to make itself part of a South African solution. The Carter years showed, however, the difficulties of 1) assembling a political base to sustain a long-term activist policy and 2) devising tactics that would actually help the move toward political freedom with minimal violence.

This is the essential background to the policy being developed by the Reagan administration. It focuses on enlisting (white) South Africa's support to bring its longtime colony of Namibia to genuine independence. As a kind of quid pro quo, South Africa is being offered an attitude toward apartheid known as "constructive engagement." Though so far undetailed, it suggests more carrot than stick.

Partly because of the change of administrations, there is a certain lull in the American debate on apartheid. Recently, however, a comprehensive report appeared that promises to become a rallying point for those who feel the United States should identify more openly with forces of all races striving for equality. "South Africa: Time Running Out," a two-year Rockefeller Foundation-sponsored study directed by Ford Foundation president Franklin A. Thomas, argues that only by so doing can the United States deny openings to Moscow and serve its own varied interests well.

The report has been received in some quarters as a challenge to the Reagan policy, but this is too simple. True, it brings a moral urgency not much visible in Washington these days. But it shares the prevailing premise that the American attitude, though important for this country, will be at most only marginal in its effect in South Africa. For instance, the perennial question of whether to cut economic ties to punish Pretoria, or to preserve them to pry out progress, is, the report realistically concludes, "not much of a choice." It is, nonetheless, the sort of choice Americans cannnot dodge. "Time Running Out" will help them make it.