France will refuse to sign new arms contracts with Libya and will not maintain "normal diplomatic relations" with that country as long as Col. Muammar Qaddafi continues to pursue "an aggressive policy" in Africa, according to Jean Pierre Cot, the French government's top expert on relations with the Third World.

Outlining a tough position toward Qaddafi as a cornerstone of the Socialist government's new policies in Africa, Cot said in an interview here that President Francois Mitterrand's Cabinet "has decided not to sell any arms to Libya because we think the Libyan policy is an aggressive one. We will honor France's signature on contracts made by previous governments, but there will be no new contracts."

Under President Valery Giscard d'Estaing, whom Mitterrand defeated in May, and the late Georges Pompidou, France sold hundreds of millions of dollars worth of fighter aircraft, naval vessels and other military equipment to Qaddafi's armed forces, which have an expeditionary force in Chad and which have intervened in Uganda, Egypt and Sudan in recent years.

Cot, who is France's minister of economic cooperation and development, also said that his government is reversing Giscard's policy of "running out" on Chad and is helping train a pan-African security force to replace Libyan troops in Chad within a year. In that time, Cot said, France will either have "helped free Chad, or will have demonstrated that Libyan troops are occupying Chad against the will of the people."

Cot, visiting Washington this week for contacts with American officials and to attend the annual World Bank meeting, emphasized however that "France is not at war with Qaddafi." Asked about reports that the United States is planning moves to destabilize Qaddafi, Cot said that he was advising U. S. officials that "it would be counterproductive to play funny games with Libya."

The same applied, he said, in Angola, where the Reagan administration is seeking to have legislative restrictions that ban aid to the rebel forces of Jonas Savimbi removed. "We are asking our American friends not to play funny games in Angola either."

In a more general context, his remarks suggested that the Socialists will not make any sizable reductions in the 8,000 to 9,000 French troops stationed in former French colonies in Africa, but their mission will be shifted away from the deep involvement in internal security and politics that has marked France's Africa policy for 23 years. Cot portrayed French troops as being assigned to Africa in the future only for regional security reasons and to protect the safety of French nationals.

"We are changing the rules on the reasons for French military presence in Africa, and we have conveyed that very directly to several African leaders accustomed to the old way of doing things," Cot said. "They have responded with great understanding to the fact that French officers will not longer be personal presidential bodyguards or local secret police."

Cot said that France would continue supplying large amounts of bilateral aid to French-speaking Africa in the face of the Reagan administation's publicly expressed doubts about the value of international aid and the Soviet Union's refusal to join in global discussions about economic reform and assistance.

"The Russians are trying to make the West pay for the economic problems of the Third World while they are content to give Africa military help and the East Germans, to do police work. The American attitude is becoming more like the Russians, except without the East Germans for the police," Cot said.

In February, in the midst of a bitter election campaign in which Mitterrand sharply criticized French arms sales to Libya, Giscard's government embargoed all dealings with Tripoli, which had sent at least 3,000 troops to intervene in the 16-year-old civil war in Chad on the side of Goukouni Oueddei.

Giscard's government then opted out of the Chadian morass by refusing support for Goukouni, son of a northern Moslem religious ruler with sympathy for the pan-Islamic Qaddafi government, and for his rivals, who previously had received French and conservative Arab backing.

Despite his campaign positions, Mitterrand approved in July the lifting of the embargo on the shipping of French helicopters, about 30 Mirage F1 warplanes and about 10 fast patrol boats to Libya as the Socialists announced they would honor all previously signed arms contracts.

Cot indicated that France would become much more actively involved in Chad now and would help Goukouni's coalition "to reconstruct a sovereign and unified Chad" and to obtain recognition from the Organization of African Unity. He said that France had agreed to help reconstruct the capital of Ndjamena "on a purely humanitarian basis."

He denied reports that French forces were training Chadian soldiers in neighboring Cameroon, but acknowledged that the French "are helping the Cameroonians train the Chadians" as part of the "logistical and financial help France will provide to an inter-African force" to replace the Libyans."

"There is no question of sending French troops back into Chad," the French Socialist political leader said in nearly flawless English. "We've burned our fingers too much in Chad to start over.

"But we must seize this unique opportunity. Qaddafi wants to host the OAU summit next year, and that means that Libyan troops should get out by then, or it will be made very clear that they are still in Chad only as an occupation force."

Saying that he had turned down an invitation from a leading Libyan political figure to have dinner "until we can have it in the French Embassy in Tripoli," which was sacked by a Libyan mob in February 1980, Cot declared that "we cannot have normal diplomatic relations with Libya as long as it remains a menace for certain friends of ours in Africa, as long as its troops are in Chad."

Qaddafi, he added, "has an enormous capacity for bluff." Even more than Adolf Hitler, the Libyan leader "can develop his influence not so much through terrorism nor through true strength, but by using an extraordinary tactical intelligence and understanding of the governments around him."