Tomorrow, Saturday and Sunday, the United States is scheduled to play South Africa in a series of Davis Cup tennis matches at Vanderbilt University in Nashville. Massive demonstrations are planned to protest the presence of a team representing a racist government, marking the first time that such influential civil rights groups as the National Association for the Advancement of Colored People (NAACP) have taken an active role in the anti-South Afirca movement.

The dates are ironic because it was on March 18, 1960 - 18 years ago Saturday - that Robert Sobukwe emerged from a caucus of the Pan Africanist Congress in Sarpeville, South Africa, with a mandate to stage the first large-scale protest against South Africa's hated - Pass Laws, which require all nonwhites 16 years of age or over to carry a stigmatizing identification with them at all times.

Robert Sobukwe was buried last Saturday in Graaf-Reinet, South Africa. From the time the Sharpeville Massacre of 69 unarmed Africans by South African police aroused world opinion on March 21, 1960, until his death, Sobikwe was under detention. He spent six years in solitary confinement.

In November 1974 U.S. Ambassador to the United Nations Andrew Young (then a congressman), Michael Cardozo (now associate counsel to President Carter) and I visited Robert Sobukwe in Kimberly, South Africa. He was then under house arrest. We listened to him for three hours as he poured out his soul and his aspirations, undampened by 14 years of detention.

He was an advocate of nonviolent protest and called for international sanctions against his country. His resistance never wavered. There would be no plea bargaining, and his philosophy today steers the black resistance movement against the racist minority government in Pretoria.

Sobukwe's last words to us in 1974 were: "When will the United States do the right thing before it's too late? There can be only one outcome here - majority rule. Go home an try to work this out."

We did, and we are still trying, but we have made discouragingly little real progress.

I bring all this up as a reminder that the real issue this weekend, the reason the civil rights groups are marching in Nashville, is not tennis but apartheid.

It was only natural that the "heavy hitters" of the civil rights struggle - the NAACP, National Urban League, U.S. Committee on Africa and the other groups that comprise the Coalition for Human Rights in South Africa - eventually would get involved in the anti-apartheid movement.

I welcome these mass-membership groups with their public relation arms and political clout because they will be able to raise the consciousness of black Americans to the problems in South Africa. I think any protests that bring the intolerable situation there to the attention of the American people are desirable.

I disagree with the leaders of the Nashville protests, however, in their position that the U.S. Tennis Association should refuse to play the matches.

I have ambivalent feelings because I have high regard for the Davis Cup as a great tennis competition. I think U.S. withdrawal from the match, and the automatic two-year suspension that would follow under Davis Cup rules, would wreck the competition.

The civil rights groups care nothing for the Davis Cup. They would just as soon sacrifice it. I do care about it, and I think there are better ways to achieve the objective of isolation South Africa - Politically, economically and socially - until she changes her unconscionable policy of racial separation.

I have discussed this at length with Franklin Williams, former U.S ambassador to Ghana and head of the Phelps-Stokes Fund, who formed the Coalition last fall.

I told him that, in my opinion, as a matter of pragmatic politics, it is better that the U.S. plays Southe Africa, beats its team, and meanwhile works through established channels to ssee that South Africa is not in the Davis Cup in 1979. USTA President "Slew" Hester has already pledged that the USTA will work for South Africa's ouster, either by voluntary withdrawal of expulsion, at the annual meetings of the International Tennis Federation and the Davis Cup Nations in July.

Ambassador Williams argues that U.S. withdrawal would be "a great symbolic gesture to the rest of the world," but let's look at what it would actually accomplish:

South Africa would advance to the next round and might even go on to win the Davis Cup, as it did in 1974 when India refused to play the final. Meanwhile, the United States would make itself inelegible for the next two years. This would remove from the scene the most powerful voice for ultimately getting South Africa out of international tennis, and at the same time would effectively ruin the Davis Cup as meaningful competition.

A far better course, I think, would be for the U.S. to push energetically for South Africa's removal for perfectly legitimate reasons: her presence in the Davis Cup is clearly disruptive and her laws clearly violate Rule 33 of the International Tennis Federation, which forbids racial discrimination. South Africa should withdraw or be expelled from the Davis Cup until her house is in order.

South Africa has been expelled by the world governing bodies of 13 sports and by the International Olympic Committee. Tennis, practically the only remaining link to the international sports community for a nation that has long been sports crazy, should become the 14th.

I think Peter Lamb, the "colored" Vanderbilt sophomore named to the South African team for the series against the U.S., should withdraw, as did his white teammate, Ray Moore, two weeks ago.

I would not play in this match if I were in top form and had been asked to play for the U.S. The emotional intensity would be too much.

I sent Lamb a telegram earlier this week urging him to withdraw because I think his inclusion on the team at this time further divides nonwhite South Africans and is a slap in the face to the 13 million black South Africans who, if the white supremacist government has its way, will one day have their citizenship taken away.

Finally, I hope the protesters in Nashville are visible, in huge numbers, and that they focus on the real issues of South Africa as elaborated by Robert Sobukwe - the need to abolish apartheid not only in sports, but in all society, and to work toward majority rule.

Until recently, I was one of many interested activists who thought that sports could be used to pave the way for social change and equality of opportunity in South Africa. We thought that if integration could be achieved in sports, for which South Africans have, perhaps, a greater fondness than any other people in the world, this would knock down the barriers to integration the rest of society.

Inddeed, this was the reasoning behind the ITF's decision to let South Africa back in the Davis Cup after it was suspended in 1970-71. It was felt there had been substantial improvements in South Africa, and that allowing her to compete in tennis would be an inducement to more.

It has not worked that way. True, South African athletes, particularly black athletes, have more freedom than they did 10 years ago. But it has become painfully clear that the Mixed Sport policy announced by Dr. Piet Koornhof, the minister of sport, on Sept. 23, 1976, has not led to anything resembling true nonracial sport, as black South Africans had hoped.

There are those who believe that the reforms and progress made in sports are significant, but I have regretfully come to the conclusion that they are nothing more than cosmetic - diversionary tactics for foreign consumption, used to conceal the dominant, hard-line repression in other walks of life.

What good is it, in the grand scheme of human rights and dignity, to say to a black South African, 'You can run in this track meet,' when he still can't vote, own a home, make a decent living, attend a school, change his residence without government permission or even walk the streets without carrying that loathsome pass?

Sports was viewed as a means to an end. The elimination of a few barriers in sport should not be allowed to cloud the evidence of how little progress has been made toward abolition of apartheid in the more important areas of South African life.

That is why so many of us are retreating from the strategy of international sports contacts as a vehicle for change in South Africa and urging neoisolationism.

The real issue is not sport. The few crumbs that have resulted from the Mixed Sports policy are too little, too late and too conditional.

The real issue is the inhuman system of apartheid. When it is legally abolished, sports will be integrated automatically. That should be the target of the voices raised in protest this weekend at Nashville.