A Soviet-built Tupolev-22 aircraft, said by France to belong to Libya, today bombed the airport in Ndjamena, the capital of Chad, in apparent retaliation for a French raid against a Libyan-built airport in northern Chad.

French Defense Minister Paul Quiles later announced that France was sending a "deterrent force" to Chad following a new offensive by Libyan-backed rebels against the government of President Hissene Habre. About 200 French air commandos arrived in Ndjamena over the weekend to supervise the flow of military supplies to the government troops and defend the airport.

Military analysts here said today's moves brought France and Libya closer than ever before to a direct military confrontation over Chad. The two countries have backed opposite sides in the 20-year-old civil war in Chad, a French colony until 1960.

Quiles dismissed today's bombing raid by a "Libyan Tupolev," flying at 15,000 feet, as ineffective, saying that only one bomb had fallen on the runway. He said the "limited damage" would not prevent French planes from continuing to land at the airport, Chad's main point of entry from the outside world.

The Defense Ministry later said two Mirage F1 fighters and a Jaguar plane arrived at Ndjamena airport this afternoon, to join four Jaguars already there. The airport remained closed to civilian aircraft.

In Tripoli, the official Libyan news agency Jana attributed the air raid to Chadian rebel forces led by former president Goukouni Oueddei. This assertion however, was discounted by military analysts here who said Goukouni's forces have no Tupolevs.

In Washington, State Department spokeswoman Anita Stockman said a single plane "of a kind known to be in the Libyan inventory" had bombed the Ndjamena airport. "Presumably it was a Libyan aircraft," she said.

She said Washington was expediting $6 million in U.S. military aid to Chad and consulting with the French and Chadian governments "to coordinate our individual efforts," as well as "consulting to see what other efforts to make."

U.S. military aid to Chad consists of providing spare parts and maintenance for two U.S.-supplied C130 transports and supplying light arms and ammunition, boots, uniforms, jeeps and trucks to its 12,000-man Army.

The bombing raids coincided with the opening in Paris of the first summit meeting of the world's French-speaking countries, with leaders of 42 states including former French colonies in Africa. The leaders of several French-speaking countries in West Africa have urged France to take tough action against what they see as the threat of aggression from Libya.

The latest French moves in Chad are the fourth direct military intervention by France in that African state since the civil war began in 1965. Quiles insisted, however, that it would quite different from the last intervention, in 1983 and 1984, when 3,000 French troops were sent to Chad.

French officials said that the new force in Chad would consist primarily of Air Force units stationed in Ndjamena. The aim, military specialists said, is to reduce the risk of casualties to French troops while increasing the ability to respond flexibly to renewed attacks by the Libyan-backed rebels.

France has accused Libya of providing logistical aid for last week's rebel offensive across the 16th Parallel, known as the "red line," which Paris has pledged to defend.

In the view of some observers, the bombing raids form part of an elaborate game of psychological and military bluff involving French President Francois Mitterrand and Libya's leader, Col. Muammar Qaddafi. The assumption here is that neither France nor Libya has an interest in getting dragged into an all-out confrontation over Chad.

With just a month to go before legislative elections in France, Mitterrand's decision to bomb a Libyan-built airfield at Ouadi Doum has generally been supported by right-wing opposition parties that are usually quick to criticize him.

The Socialist president has sought to exploit a wide consensus on most foreign policy issues to press his claims to be allowed to complete his seven-year term of office in the event of a right-wing victory in the elections.

Today, Quiles denied a Libyan claim that the Ouadi Doum airstrip was a civil airport used to ferry food supplies to famine victims in northern Chad. He said it was "a military base and equipped as such." The Defense Ministry said the landing strip was damaged in six places in Sunday's bombing raid by French Jaguar aircraft stationed in the Central African Republic.