A GRAND NOVEL of diplomatic intrigue in Africa awaits its author. Josef Conrad could do it properly but, alas, he is with the departed. Graham Greene might be an adequate substitute but he is disengaged somewhere in Europe. So the field is open for a chronicle of one of the most fascinating international machinations of our time.

It is unfolding on two dramatic levels, the symbolic United Nations one where words may substitute for reality, and another, clandestine level where national, military and corporate destinies will be determined.

The immediate subject is Namibia, an obscure slice of the African continent that not one American in ten thousand could identify on a map. The very obscurity of the thing enriches the tale and enables great and small powers to engage in secret and subtle maneuverings unhindered by the sound and light shows of the nightly news.

The ostensible point of it all is the creation of a new Namibian nation, free of the South Africans who have occupied the land since wresting it from the Germans in 1915. But there is more on the table than that. American influence and prestige in Africa are at risk. For different reasons, the same is true of the Soviet Union and Cuba. The fate of Angola, Namibia's northern neighbor, will be influenced heavily by the outcome. The United Nations, Western Europe and Canada have hands in the game. Human greed is not absent from the equation. Vast mineral deposits are involved, among them diamonds and uranium. And overlying all this are the visceral issues of race and colonialism. Namibia is the last colony on the continent.

For decades the Namibian question has been as intractable as the Palestinian question. The League of Nations wrestled with it to no end. The United Nations has been involved, fruitlessly, since its creation. A 16-year war of liberation by the guerrilla army of SWAPO (Southwest African People's Organization) has been futile in breaking South African rule.

Today a solution is in sight but only if delicate and intricate arrangements now in process somehow can be made to hold. The United States, through historical accident, is at the center of that process. The Germans are more logical candidates for the role. They created the colony in the late 19th century and slaughtered more than 60,000 tribesmen before they were done. But that was long ago and, presumably, they lack leverage today.

The South Africans could supply an easy solution by withdrawing. But neither world opinion nor U.N. resolutions have persuaded them to that course. Armies might be raised to drive them out by force but no one has shown a taste for the large war that would involve. So the Americans, innocents in Africa, have become the middlemen in concert with France, Britain, Canada and West Germany. They call themselves the "Western contact group" and they are employing the tactic of special interest politics: something for everyone.

Their first task is to secure from South Africa, SWAPO and other Namibian political forces an agreement on a U.N. plan for free elections, the disengagement of military forces and the creation of an independent black government free of South African control. They must also secure the blessing of the nearby African states.

The various elements of this plan are falling into place and a final agreement is now plausible. SWAPO's reward for cooperation probably will be Namibia; it is the political faction most likely to win an election and inherit the land. That result also would satisfy the nearby states; Namibian independence -- under SWAPO -- is one of the two unresolved political issues on their agenda. The other is the liberation of South Africa itself.

On the face of it, South Africa gets nothing from the arrangement except financial relief from its present subsidies to Namibia and from the heavy cost of its war against SWAPO. An intangible bonus might be a dollop of international goodwill, but the South Africans, like the Israelis, put little stock in that commodity. Why, then, would they settle? The answer lies in a hidden agenda on which the entire enterprise depends. Angola is the key to it.

South Africa today sees on the Namibian border a "communist menace," a tangible threat to its security. Those fears arise from the seven-year presence of 15,000 to 20,000 Cuban troops in Angola and from the substantial economic, military and political influence of the Soviet Union in Angolan affairs. The removal of that menace is South Africa's price for Namibia. It is not an element in the U.N. plan; it is not even publicly acknowledged as a quid pro quo. But it is the heart of the affair, the final move in this African chess game.

For Angola, there are certain advantages in such an arrangement. The rental army from Cuba is costly to the Angolans; the bill may be as high as $500 million a year. Furthermore, the stated reason for the Cuban troop presence is to protect Angola from South African troops who regularly invade the country to attack SWAPO sanctuaries; even now the South Africans occupy a large chunk of southeastern Angola. If the SWAPO-South African war is ended and if South Africa withdraws from Namibia, there would be, presumably, no further need for Cuban protectors.

Another payoff to Angola could be recognition by the United States, which has been denied since that nation gained independence under a Marxist government in 1976. With U.S. recognition, financial assistance could be forthcoming. It is desperately needed. The Angolan economy is in a state of near-collapse.

How the Cubans and the Soviet Union might profit from this deal is something of a mystery. Angola is one of their major footholds in Africa and, in geo-political terms, that is probably important to them. But approaches have been made by the Americans and words have been spoken. Alexander Haig, before resigning as secretary of state, discussed the problem with Soviet Foreign Minister Andrei Gromyko. Haig also met with the vice president of Cuba. There have been other secret contacts. Would an agreement ease the cold war between the United States, the Soviets and Cuba ? There have been hints to that effect but nothing more.

There is yet another piece to the puzzle -- UNITA, the guerrilla army led by Jonas Savimbi in South Angola which seeks to overthrow the Angolan government in Luanda. There is a body of opinion that UNITA poses a far greater threat to the Angolan government than South Africa does and that the real purpose of Cuban troops in the country is to prevent Savimbi's triumph. Savimbi has sympathy and support from South Africa. He has friends in the Reagan administration. Would he be abandoned as part of the Namibian settlement or make peace with Luanda?

No one but the participants know what messages and promises are being carried back and forth by various American emissaries, such as roving Ambassador Vernon Walters, Chester Crocker, the assistant secretary of state for African affairs, and Crocker's deputy, Frank Wisner.

Frenchmen, Germans, Englishmen, Britons, Canadians and Africans are carrying on their own dialogues. People huddle in rooms at the United Nations, make mysterious flights to Paris, Lisbon, Pretoria and Luanda. There are heavy discussions in the boardrooms of oil and mining corporations. And almost certainly there have been secret contacts in the African bush.

Of course there's a novel here, awaiting not only author but an ending.