THE CARTER adminstration's response to the trouble in Zaire strikes us as on the money. To meet the emergency of some 2,000 European civilians reportedly threatened by the rebels who have crossed from Angola, the administration made 18 transport planes available to France and Belgium, whose nationals they are; the handful of Americans in the battle zone had already reached safety. Although there are reports of some tens of European deaths, rescue operations are under way. Then, to make a gesture of support to the again-embattled regime of President Mobutu Sese Seko, the United States promptly offered $20 million worth of "non-lethal" aid (spare parts, communications gear, petroluem, etc.). Zaire's soldiers have moved into action against the insurgents. There is time to see what else the United States might usefully and feasibly do.

Meanwhile, Fidel Castro has called in the chief American diplomat in Havana to say that Cuba is not taking direct or indirect part in the Katangese incursion into southern Zaire. The United States followed by stating that Cubans in Angola had armed and trained the Katangese. Whether that contradicts the Castro assurances isn't clear. (Zairian and French reports, we note, assert that Cubans and Russians are present in Zaire proper.) But it is, as the diplomats say, interesting that the Cuban should take the initiative he did. It suggests at the least an intent to soften the confrontation that has been building between Washington and Havana since Cuba's African adventure began two or more operations ago. None of the nationalist political claims that the Cubans used to justify their policy in Angola and Ethiopia are relevant to Zaire, where the Katangese are secessionists and marauders, nothing more.

It will surely take more to be sure that Cuba gets the message that the United States won't stand still for repeated Havana-sponsored and manned interventions in Africa. There are, however, a couple of other avenues that the Carter administration has been exploring. One we don't much care for. That is the reported attempt to find a legal way to engage in clandestine operations in support of forces opposing the Cubans in Angola and Eritrea. We can't imagine that clandestine operations would stay clandestine - the story that they are being studied proves the point - or that they would be effective. What is done in Africa ought to be done openly. Given the public's raised consciousness of the Cuban-Soviet role, we do not think the administration would have great difficulty gaining public support for a well-conceived military-aid operation in critical African situations. We have in mind support of besieged friendly governments, as in Zaire.

There is another avenue, represented by Zbigniew Brzezinski's current trip to Peking. The Chinese have their own reasons to counter what they see as Soviet expansionism in Africa, and their own resources. On the eve of the White House aide's arrival, they condemned attacks by "mercenaries directed by the Soviet Union and Cuba." Others, such as the Saudi Arabians, also have their own reasons and resources. Until now the Chinese and Saudis have felt that the United States was not taking the African problem seriously. It is apparently one of Mr. Brzezinski's purposes in Peking to demonstrate otherwise. If he can, then it becomes possible to imagine various forms of cooperation designed to slow the Soviet-Cuban momentum in Africa. Its leadership responsibilities do not require the United States to do everything itself. They do require, however, that this country provide a political context in which others will feel encouraged to do what they find essential to their own national interests.