PARIS -- Nelson Mandela arrives in America riding the crest of a mighty wave of change in South Africa. Caught in the backwash at home is President F. W. de Klerk, his head barely above water. Celebrate Mandela during his American odyssey, but do not lose sight of de Klerk's bobbin' noggin. More than ever, the two South Africans need each other if apartheid is to follow the Berlin Wall into history.

The Mandela tour is a hectic, celebrity-centered dash through eight American cities. For some U.S. liberals left on the sidelines, the scheduling has bruised feelings and raised legitimate concern about the trip's impact on Mandela's health and dignity. But the charge that the Mandela tour is being ''hijacked'' by black pressure groups and white Hollywood stars for unworthy goals is a chimera. Mandela arrives with his own agenda, which each moment of the tour is intended to advance.

Mandela is not a man to be hijacked, as he demonstrated in surviving a quarter-century in prison without losing his seriousness of purpose or remarkable political skills. Both qualities will be on constant display in the United States, as they were during a 10-day tour of European capitals in advance of his arrival in America.

On this side of the Atlantic, Mandela was all business. He quietly lobbied leaders to reject a British-inspired move to lift economic sanctions against South Africa at the European Community's summit meeting in Dublin next week. He persuaded West German Chancellor Helmut Kohl and others that it was too soon to end sanctions as a reward to de Klerk.

Mandela is using his American and European trips to demonstrate that the African National Congress controls the sanctions issue as it prepares to open negotiations with the white Afrikaner government over a new constitution and sharing power. He must show the restive white electorate in South Africa that the country can escape international sanctions only by coming to terms with the ANC.

That is one of two immediate ANC needs Mandela will pursue in the United States as he pays tribute to the African-American, labor and other constituencies that have supported strong sanctions and can be counted on to continue this pressure. The other need is to raise money, the purpose of enlisting so many American celebrities in the Mandela tour.

The ANC, legalized in February when Mandela was released from prison, has a huge following but no organization in South Africa's townships. To open offices and staff them, to bring home refugees and to do the other things that will establish the movement's domestic presence and legitimacy will take enormous sums of money.

These are important items on the agenda of ending apartheid by peaceful means. They are necessary; but they are not sufficient, as Mandela knows better than anyone. Creative and brave leadership in the white community is also needed to guide South Africa to a democratic political system and equality of opportunity. The most subtle task facing Mandela on his American trip will be to use it to reinforce de Klerk's position as well as his own.

Members of Congress and others who have been opposing a de Klerk trip to Washington to meet with President Bush are more royalist than the king on this issue. Mandela does not oppose White House exposure for de Klerk. There is reason to believe that he sees such a journey as a suitable reward for the progress that de Klerk has made, while keeping sanctions in place.

De Klerk toured Western Europe last month and came home able to argue that South Africa's long international isolation is ending thanks to his reforms. The ANC could have easily turned out hostile mobs at each of de Klerk's stops, as it has in the past. But Mandela's organization refrained this time. There is an understanding in the organization that weakening de Klerk's standing at home at this point benefits no one.

De Klerk is confronted by an alarming growth of the pro-apartheid Conservative Party at the polls, and increasing threats of an armed rebellion by other white extremists if he opens electoral rolls to the black majority. Despite an ambiguous speech in April that was wrongly interpreted as a retreat on reform, de Klerk continues to move in the direction of ending apartheid. He frequently speaks in code. All politicians do.

But the change is unmistakable for anyone who has watched the Beloved Country's politics during a long period of time. Now the white government uses deceptive language to try to minimize at home the change it is sponsoring, just as its predecessors used deceptive language to try to maximize abroad the change it was avoiding.

De Klerk has cracked the old pretense by whites that they alone would decide the future of South Africa. Mandela struggles to prevent a new black version of racial ideology from taking root in South Africa. The future of South Africa is a joint venture. Mandela's visit to the White House is a well-deserved moment of triumph and of promise for him and for the white South African leader who helped make it possible.