THAT WAS QUITE a bolt that France hurled at South Africa: a three-pronged announcement of recall of the ambassador, suspension of new investment and introduction of a United Nations condemnation of the regime's state of emergency. At one stroke, the French took the hardest or at least the most conspicuous position of any Western state. Observers link the new French position to a decision by the Mitterrand government, facing elections, to adopt a genuinely leftist stand on at least one major issue. It is a diplomatic event all the same.

We confess to a certain envy in viewing the French position. Skeptics ask what the angle is and point out that unrest in South Africa is a greater damper on investment than any act of Western self-denial. Still, no one can be in doubt about where the French stand on apartheid. Whereas five years into "constructive engagement," many Americans and almost everyone elsewhere suspect the United States is cozying up to apartheid. The administration has some sophisticated rejoinders, but it must fight its way upstream against the unmistakable impression of permissiveness left by the president, who can seem impervious to black victimization, and the State Department, which becomes increasingly defensive. "America is anathema to people in South Africa now," Sheena Duncan, a white South African long associated with the anti-apartheid Black Sash movement, told a Washington audience yesterday. Her words cut.

The terms of the West's argument over sanctions are changing. South African rigidity and American ambivalence play off each other. We happen to think the administration is right in claiming that sanctions -- not just the threat of them, but the reality of them -- are less likely to pressure whites toward reform than to slowdown the economy, a powerful engine of black advancement. But with the administration's own commitment to ending apartheid under a cloud, its resistance to sanctions gives sanctions a good name. Congress is moving toward some form of sanctions -- watered-down perhaps, but precedent-setting.

If there is a legitimate argument over sanctions, there can be none over the value of bringing the West's moral authority to bear. Remote, lonely and frightened as well as proud, white South Africa craves inclusion in the company of the West. This gives Western words and gestures uncommon importance. The Reagan administration has dissipated much of the leverage available to the United States. Briefly last fall it seemed as though the president had found his voice -- the American voice. The effect was electric, but there was no follow-up. Where is the American voice?