IT'S NOT A state visit. He is not a head of state. But when African National Congress leader Nelson Mandela arrives in New York Wednesday, he will be treated with a deference normally reserved for the most powerful world leaders. For many here Mandela's trip will surpass in importance Soviet leader Mikhail Gorbachev's recent state visit to Washington, for it is spiced with the emotion of black American politics. Mandela -- freed from his white oppressor's jail in South Africa -- has become not only the leader of black South Africans but also a reminder to American blacks of the uncomplicated days in this country when fighting white racists was the one and only issue on the black agenda.

Adulation in the United States is a mixed blessing for Mandela. His international stature strengthens his bargaining position in South Africa at a critical moment in the fight to end apartheid. But it could also trigger trouble. If a steady diet of ticker-tape parades and hosanna-like tributes gives Mandela the sense that he holds control over U.S. foreign policy decisions on South Africa -- especially on the delicate issue of sanctions -- it could push Mandela in the direction of hard-line negotiation.

And an inflexible bargaining stance could destroy the fragile opportunity that now exists to achieve a political settlement and give blacks full rights as citizens of South Africa. Should negotiations fail and civil strife erupt, Mandela's chances of accelerating his country's economic growth and extending its benefits more equitably would be doomed as well. The opportunity of an historic moment would slip away.

This rare moment exists because a black leader -- Mandela -- and a white leader -- President Frederik W. de Klerk -- are both intent on negotiating a peaceful solution to the racial conflict that tortures South Africa's soul. Each is dependent on the other for accommodations that will allow them to claim victory to their separate constituencies. But time is running out for both as conservative whites challenge de Klerk for moving too fast and militant blacks put pressure on Mandela for going too slow.

"The two personalities are key and make this a very critical time in South African history," said Thomas Karis, editor of a four-volume history of black South African protest against apartheid. "The alternative is bloodshed."

"What Nelson Mandela has done is make it an acceptable tactic for South African blacks to sit in a room with a decades-old enemy and talk," said Randall Robinson, executive director of TransAfrica, the anti-apartheid lobbying group. "That is no mean feat in a country run with violence and distrust."

The other part of that equation is that de Klerk has taken the risk of being Mandela's white partner.

"Both leaders can lose out," said South Africa's ambassador to the United States, Piet Koornhof, " but neither can win without the other winning. Americans have to understand that by helping both Mr. Mandela and President de Klerk, they will be helping the moderates in South Africa and ensure that radicals on the left and right do not prevail."

U.S. policy toward South Africa has been torn between domestic and foreign policy considerations. Thus far, the Bush administration's policy has not amounted to much beyond standing pat in hopes of avoiding any initiative that could stir trouble with black Americans as did the Reagan administration's widely-denounced policy of "constructive engagement."

Within the administration's foreign-policy circles there is considerable support for lifting some U.S. sanctions against South Africa. "You will not find many in the administration who support the idea that . . . sanctions should not be lifted to encourage the South African government to engage in serious talks," said Georgetown University's Chester Crocker, the former assistant secretary of state for African Affairs and architect of the constructive-engagement policy.

Crocker argues that lifting the sanctions would actually strengthen Mandela's hand. "There are many people who respect Mandela inside South Africa as the senior father figure of the movement. But there are also many blacks who question his instincts and timing . . . . The only way they will be convinced of his leadership is if he can get de Klerk to meet him halfway," he said.

"Bush and Baker have taken no position on whether sanctions should be lifted out of a desire to avoid any domestic trouble on this issue. That's why we have to decide the extent to which this is a domestic issue or a foreign-policy issue before the administration can make a decision. I think the debate should play out in South Africa, not here."

But there is no doubt that Mandela is at a distinct disadvantage in negotiations with a powerful white government with a history of brutal repression.

Randall Robinson argues that any U.S. decision on sanctions or other aspects of foreign policy toward South Africa should reflect that reality as well as black America's unalloyed support for Mandela -- and Mandela wants the sanctions left in place.

"Mandela is passionate about the need to sustain sanctions until they turn the corner in negotiations, which have not begun in any substantive way," said Robinson. "They are still having talks about talks. There is no indication that the government is ready to do what's necessary for a solution -- release the 3,000 political prisoners still in jail . . . . De Klerk has shown no commitment to solve the real problem, which is one-person, one-vote. He has still got to repeal the Group Areas Act, the Land Act and what remains of Separate Amenities."

Robinson also argues that "sanctions are de Klerk's best friend. He can say to the right wing that sanctions are killing us and successful negotiations are the only way out -- the only way to get rid of sanctions and to be restored as members of the international community."

Robinson also favors U.S. help for the African National Congress in financing its budding organizing efforts inside South Africa and in building a fund to compensate white capitalists scared by Mandela's talk about nationalizing sectors of the economy. Pressure for unquestioning support for Mandela extends beyond the issue of sanctions. For example, Prof. Robert Price, author of "The Process of Political Transformation in South Africa," believes the U.S. business community should resist the urge to debate with Mandela about his push towards a nationalized or socialist-style economy and simply follow Mandela's lead.

"What we shouldn't be doing is lecturing Mandela on economic policy," said Price, who teaches political science at the University of California at Berkeley. "The tendency here is to believe free-market intitative is the savior of everything. But black South Africa needs both economic growth and economic redistribution, and they {the ANC} want to keep their options open."

But administration officials say Mandela could use a lecture in economics.

"South Africa's future is best assured by a free market," said a senior State Department official. "Controlled economies around the world have demonstrated their incapacity to be useful. We would hope as he goes around the world that he and others involved with serious thinking about South Africa's future would get off their rhetorical jags and what they learned at the London School of Economics and face the reality that free markets offer the best hope for increasing the economic pie."

Michael Christie, director of the Washington office of the South Africa Foundation agrees: "Mandela faces the dilemma of having to satsify the understandable demands of his constituency -- black South Africa -- by handing out what I call the 'Liberation Dividend' at the risk of damaging the ability of the economy to generate sufficient growth to satisfy the economic aspirations of 40 million people inside South Africa's borders." Christie points out that the South African economy has been stagnant for 15 years and that Mandela very much needs massive foreign investment -- which he is unlikely to attract if he pursues the failed economic policies of Eastern Europe and insists that U.S. economic sanctions stay in place.

"Mandela is a great man and a hero but he is also a politician and he is trying to maximize his power," the State Department official observed. "It is important that we make our own decisions about how best to move negotiations along. We have a good deal of appreciation of de Klerk's problem, and while sanctions cannot be relaxed today it does not mean they can't be relaxed tomorrow." The recent postponement of de Klerk's planned visit to the United States put this tension in U.S. policy in sharp focus. Despite an invitation from President Bush to both de Klerk and Mandela to visit the United States -- and Mandela's statement that he did not object to de Klerk's visit -- the trip was postponed because some black American groups objected to de Klerk visiting in advance of Mandela and planned massive demonstrations.

But if de Klerk is to withstand right-wing opposition even to talking to the ANC, he needs some form of recognition and support from the United States. In a recent election in Umlazi, de Klerk's Nationalist Party won by just 547 votes; three years ago it won by nearly 5,000 votes. Inside the Bush administration, consideration is being given to offering de Klerk some support by lifting landing rights for South African Airways and helping South Africa begin to normalize relationships with international banking organizatons. But any such decision would likely stir black protest in the United States.

Yet the right combination of tolerance and pressure by the United States could be crucial to both Mandela and de Klerk in taking advantage of what virtually all observers agree is an extraordinarily promising -- but perishable -- set of circumstances.

"I think what you really have here is a number of factors that have never been present before," said Pauline Baker, a senior associate at the Carnegie Endowment for Peace who has just returned from a two-week trip to South Africa. "For the first time, political dissent is legal in South Africa. There is more tolerance for ideas now, more free flow of ideas . . . . There are splits among blacks and splits in the white camps, so people realize they are going to have to compromise."

Baker points to another important change in the external environment surrounding the South African negotiations, "specifically the collapse of communism." Because of the receding of Soviet power, there is no longer a threat that weakening the white South African structure would provide an opening for communist rule. "It means," said Baker, "the debate in South Africa today is internal . . . and South Africans are not looking outside and away from the issue of apartheid."

"Most important of all you have two leaders committed to negotiations," she added. "This is a truly rare event. Look at the Middle East with Shamir and Arafat, a situation of total and direct confrontation. The current willingness to talk makes this a unique situation in South Africa." All of this puts enormous pressure on Mandela. In his own country, he is a legend -- a man who had been in jail 27 years, far longer than most black South Africans, whose median age is 17, have been alive. Mandela's stature is the single thread holding black political opinion together and making negotiations with whites possible. That legendary status also fuels the emotions evoked by his visit here.

For black Americans, Mandela, as the personification of the black struggle against white oppression -- Martin Luther King Jr. returned to life. Mandela is a comfortable throw-back to the relatively simple struggle of black against white over the inequities of racial segregation.

"I expect African Americans will respond to Mr. Mandela with the same warmth and affection that Africans responded to Dr. Martin Luther King Jr.," said Benjamin Hooks, executive director of the NAACP, in a statement he released on Mandela's visit.

Mandela is also a unifying force among American blacks at a time when class differences, political fights and a widening gap in generational perspectives is weakening the racial bonds that once held black Americans together.

When I met Mandela in South Africa in February, he was curious about America's handling of black people. He wanted to know if the racial situation was as good as he imagined from press reports and from what he had heard about the lives of famous black Americans, such as his favorite fighter, Mike Tyson. He was curious to know if black children could get a good education and the extent of political awareness among blacks now that legal public segregation had ended.

Unlike most black American leaders of his age, Mandela did not come from the church tradition of ministers as civil-rights leaders. He is a trained lawyer, cautious in his speech to the point of being pedantic. He is wonderfully patient and courteous about autographs and pictures, shaking hands with everyone from school children to the chauffeurs of the dignitaries who came to see him.

He is also different in his easy bond with whites; Mandela lacks any bitterness even toward his white jailers. In fact, he befriended one jailer and has visited him since leaving prison. Mandela speaks of the system of apartheid -- never of white people -- as his enemy. At the start of recent talks to arrange formal negotiations, Mandela even spoke in Afrikaans to reassure South African whites. Mandela's personal grace and legendary status have been put to the test, however, by recent events. Soon after his release from jail, Mandela failed to persuade the United States and Sweden to intensify sanctions against South Africa. He has been unable to form an alliance with Mangosuthu Buthelezi, prime minister of the Zulu people and head of the Inkatha movement. Fighting between Buthelezi's loyalists and the ANC continues despite Mandela's plea to his supporters to throw their weapons into the sea and "close their death factories."

The South African stock market took a dive after Mandela spoke about nationalizing industries and committing himself to continue violent struggle in South Africa. And he has failed to get black South African children to return to schools, one of his most impassioned pleas immediately after his release.

Mandela is also struggling to build an organization for the ANC inside South Africa in the few months since the anti-apartheid group was legalized. In April he admitted that some members of the ANC had been tortured by ANC leaders. Health problems and a heavy schedule of travel have further diverted his attention as he prepares for the next round of talks with the de Klerk government.

Still. Mandela remains a singular figure in South Africa and on the world stage. The question for America is how to embrace Mandela for all that he has achieved and can still achieve, without transforming him into a icon, unable to deal pragmatically with the momentous task of transforming a society without destroying it.

Juan Williams writes frequently on politics for Outlook.