Thumping the dusty couch in his appropriately shabby embassy, a delegate from one of Africa's poorest nations gave this terse preview of the international extravaganza to be held here Monday, the first Afro-Arab summit conference:

"Of course we'll have political agreements and technical agreements and we'll all support the Palestine cause. But what about the money? The message will be put to the Arabs that it's time for them to go beyond declarations and promises."

It was phrased even less delicately by an Egyptian diplomat. "If you want to know the truth," he said, "nothing is going to come of it except a big fight. The Africans are fed up and they are going to come in here asking for a lot of money.They're not going to get what they want."

At least 60 countries are expected to participate in the three-day conference, which is to be opened by Egyptian President Anwar Sadat.

The planners of the gathering, who have been working on it for more than two years, envisioned it as the forum where Arabs and Africans, after centuries of fluctuating relationships, would formalize a new partnership in politics and development.

That is surely how it will be portrayed in the official announcements, but it seems likely that the unpleasant subject of money - Arab wealth, oil prices and African poverty - is going to split the participants. The gap between diplomatic rhetoric and reality, between pomp and performance, is expected to be a wide one.

That pattern has already developed in three days of preliminary talks among the foreign ministers of the participating countries. While the discussions on political matters and on procedure are reportedly going smoothly, they are understood to be having difficulty in finding a formula that will paper over the apparently wide divergence on economic issues.

It might appear that there is little in common between, say, an improverished black African state populated by Christians and run by leftists and the rich Arab oil states populated by Moslems and run by conservative princes. But Arabs and Africans have had links of one kind or another for centuries, from the slave trade to political alliances and they have shared the experiences of colonialism, underdevelopment and emerging nationalism. Countries like Egypt and Algeria, which are Arab and African and were early leaders of the nonaligned movement, bridge the gap between them.

For Egypt, the chance to be host at a conference called to weave together all these threads for the common advancement of Arabs and Africans is an honor that fulfills Gamal Abdel Nasser's vision of this country as a leader of both groups.

According to Sayed Nofal, acting secretary general of the Arab League, "the Arabs and the Africans are not trying to create a new international bloc. Their cooperation falls within the general stream of Third World cooperation which brings together developing countries from all continents."

He said that "Afro-Arab cooperation is not directed against anyone. It seeks to build, not to destroy, and to create greater harmony in the world and a better atmosphere for general peace." Relations between the two groups, he said, come from "deep in the past and look forward far into the future beyond such temporary problems as the racist regimes of foreign settlers in the Middle East and Southern Africa." This is a reference to Israel, which formerly had good relations with several black African states but now has few African links outside of its close relations with white-ruled South Africa, and to Rhodesia.

The question facing the conferees is whether the lofty sentiments expressed by Nofal can prevail over the collective African unhappiness over what they feel is an inadequate level of economic assistance from the oil-producing Arab states and over the failure of the oil producers to give the poorest nations a break on oil prices.

As long ago as 1974 such prominent African leaders as Mobutu Sese Seko of Zaire and Julius Nyerere of Tanzania were warning that Afro-Arab relations, then at their warmest, would be set back if more help were not forthcoming.

The Africans are pushing a proposal drafted by Tanzania for a minimum of $2 billion in development aid from the Arabs, and are also understood to be seeking changes in the way whatever aid is given is allocated and controlled.

Many African leaders want the Arabs to stop favoring the Moslem countries with their aid. A Libyan grant of $4 million to Niger for the construction of mosques and instruction in Arabic is cited as an example of the kind of aid the African find helpful but irrelevant to their real needs.

The Arab response is likely to be cool, informed sources say. Reports from the foreign ministers' meeting say that in the interests of harmony, there may be a compromise in which the Arab states will increase the capital of development banks in the Sudan and the Ivory Coast, but probably by far less than the Tanzanian demand.

"African aid hopes tend to exceed reality," said an Arab diplomat involved in the conference preparations. "Some might use this opportunity to talk about more money. That's fair enough. The only way you can get money from the Arabs is at the top, so perhaps this will create an atmosphere for more aid."

The Arabs generally say they are already doing more than their share to help the black African states, certainly more than the industrialized countries are doing. Nor are the conservative, rigidly anti-Communist states like Saudi Arabia and Kuwait interested in giving aid that will shore up some of the radical African regimes. Furthermore, there are Arab states closer to home, especially Egypt and Sudan, that have a higher claim on aid from the oil-rich nations.

The Africans appear to have little leverage to use in trying to extract more aid from the wealthy Arab states. There is always the implied threat that they will resume their once-good relations with Israel, but it is hard to reconcile that with the claim of both Arabs and Africans that those relations were broken out of principle, not because the Africans were bought off.

There is no shortage of local or regional disputes and conflicts that are expected to be discussed at the conference, such as Benin's charges that Morocoo participated in an abortive invasion there are Sudanese support for the Eritrean separatists in Ethiopia.

Nofal said none of these will be on the formal agenda, which is being prepared by the foreign ministers. "The nature of the conference does not allow for local disputes to be formerly raised in discussions," he said, but these parochial disputes are bound to come up in the meetings.

Experienced observers of African affairs said the atmosphere was unlikely to be enhanced by the publication in Egypt's foreign-language press this morning of a long analysis of the decision by King Hassan of Morocco to pull his country out of the Organization of African Unity.

The dispatch, attributed to the Associated Press, asserted that tribalism, dictatorship and tyranny have taken hold in many parts of the African continent where "the very fabric of civilized life seems to be disintegrating." It also says the OAU secretariat has been infiltrated by leftists under Soviet influence - a fear that many conservative, anti-Communist Arabs already harbored.

Just by listing the names of the countries whose delegates are arriving, the local press is giving some of the expected exotic flavor of the summit conference: The Central African Empire and South Yemen, Swaziland and Lesotho, Mauritius and Bahrain. But it is still not known for certain which heads of state will actually be present.

Some of the more unusual African personalities, such as President Idi Amin of Uganda and Emperor Bokassa I of the Central African Empire are expected. Col. Muammar Qaddafi of Libya is not. Saudi Arabia's King Khalid is in a hospital in London and Iraq has sent word that its president, Ahmed Hassan Bakr, will not be here.

In any case, the conference is going to create a logistical nightmare in Cairo, a city that functions only fitfully in the best of circumstances.

As part of the tight security measures, the heavily traveled Nile Corniche has been closed to non-conference traffic, throwing the rest of downtown into worse chaos than usual. The delegates are virtually sealed off from the populace and from the press.

But the city has primped as best it can, down to a new coat of red paint around the tree boxes on the airport road. Most of the trees, unfortunately, died long ago.