Libya has replaced Cuba as the leading worry in Africa for France, the most active Western power on the continent.

Wherever the French move in Africa these, days, they seem to find the Libyans across their path, complete with Soviet arms.

As ardent Moslem, Libyan leader Muammar Quaddafi does not profess goals identical to the Soviets, but the Libyan describes himself as a revolutionary and finances and trains such radical Marxist groups as the most violent wings of the Irish Republic Army and the Basque separatist movement.

While Qaddafi's views do not match the Soviets' as closely as those of Cuba the Libyans and Soviets seem to have established a close working partnership through much of Africa.

Some official sources here suggest that Qaddafi is prepared to offer the Soviets a naval base on Libya's Mediterranean coast.

Libya's destabilizing actions in Africa are a concern not only to France, but also to its African client-states and, increasingly, to the former British colonies in West Africa. The English-speaking West African governments of Nigeria and Ghana have been drawing closer to France as a shield against the Libyans.

French worry about Libya seems to be so great that it is serving as one of the motivations for a rapprochement between France and Egypt, who have been on bad terms over French hostility to the Camp David Israeli-egyptian peace accords. The two have a common interest in counteracting Qaddafi. Observers here see this as one of the most plausible explanations for the distinct softening recently of France's negative statements about the Camp David accords.

Even though Libya has a population of only 2 million, it uses its oil revenues of $1 billion a month to finance, train and arm a large variety of opposition movements. Qaddafi's moves since his abortive attempt to help Uganda's Idi Amin stay in power show that Libya was not daunted by that military setback.

The Libyans are having growing success among the large black Moslem minorities in sub-Saharan Africa in depicting France as an obstacle to the spread of Islam. But Libya has not hesitated to back non-Moslems against Moslems.

As one French official recalled, "When we switched our alliances in Chad and got together with the people from the north, we found the Libyans switching their alliances to the people in the south, even though the northerners are Arab and Moslem. Whatever move we make, the Libyans do its mirror image."

The latest example of Libya moving in tandem with the Soviets is the way Qaddafi was building up Libya's presence in Emperor Bokassa's Central African Empire before last month's coup. French spokesmen say 200 Libyans were the Central African armed forces and that the arms caches they left behind included 6,000 Soviet-made Kalashnikov submachine guns found at Bokassa's imperial palace.

French sources say that the Soviet Embassy in the Central African Republic's capital of Bangui is one of the largest in the world, with a staff of 150 in a country of fewer than 4 million.

The French say they have confirmation from a Central African minister, who took part in the negotiations that Bokassa was conducting in Libya when he was overthrown, that Bokassas was offering Gaddafi two strategically located former French bases in Central Africa. They are Ndele in the north near the Chad border and Bouar near the southern frontier with Cameroon.

The bases would have given Gaddafi and his allies the capability to intervene in areas that the French see as vital to their interest, notably against Gabon and Niger, the main sources of uranium supplies for a French nuclear energy program that is France's most important answer to the world oil squeeze.

The offer of the old French base at Bouar also would have allowed the Libyans to leapfrog the psychological and physical buffer zone of the Sahara into the heart of French-speaking black Africa.

Qaddafi has even offered on several occasions to by the uranium mines of Niger.He also reportedly expressed interest in mining operations for various minerals in Guinea, Zaire, Mauritania and Upper Volta.

The French insist that the Central Africans Republic's uranium, much vaunted by Bokassa, was not really economically reasible to exploit. But the country's hinge position makes it a good place to strike out for the uranium that is of interest.

French concern in the area is demostrated by the decision to name a colonel who was the head of the Africa division of SDECE, the French intelligence service, as the new ambassador to Gabon.

A visit by Saudi Arabia's King Khalid to Libya last week is seen here an effort to moderate Qaddafi and draw him away from the Soviets, but French officials express pessimism that the Saudis will have much effect.

French relations with Libya have been, as a high French official put it, "ambiguous" for years. The French have sold Libya large numbers of Mirage jets, military helicopters and air defense rockets. They are currently delivering rocket-launching patrol boats and landing craft to Libya.

Yet, despite his frequently renewed request, Qaddafi has not managed to get himself invited for a state visit to France. French officials say that Qaddafi never fails in his frequent messages to French President Valery Giscard d'Estaing to speak of his admiration for the French revolution.

France also has reacted with cautious refusals to Qaddafi's offers to make Libya one of France's main oil suppliers.

As a former desert nomad, Qaddafi for years has been seeking influence and leadership over the Sahara tribes of northern Mauritania, Mali, Niger and Chad in an east-west belt in the French sphere of influence.

One result is that President Seyne Kountche of Niger, for instance, has taken special care to keep the tone of his relations with Qaddafi as friendly as those with France, French sources say. Like the other countries in the zone, Niger is split between the desert Abrabs of the north and the blacks of the south.

With the help of morocco and Egypt, France can probably contain Qaddafi's ambitions in the Sahara. Algeria, which often has expressed its private annoyance over Qaddafi's attempts to appear more militant in Sahara affairs than the Algerians, also has convergent interest with France in countering Libya.