The Carter administration sent an emergency airlift of military and medical supplies to Zaire yesterday to help repel what that nation labels "an invasion" by Cuban-led "mercenaries" across the Angola-Zaire border.

It was the first involvement of the Carter administration in a foreign shooting conflict.

Administration officials insisted the U.S. role is minimal, limited at present to about $1 million in accelerated deliveries of previously authorized military aid to a major African recipient of U.S. support. At the same time, American officials claimed their knowledge of the conflict is very limited and that they have "no confirmed, solid evidence" that Cubans in Angola are involved.

Despite the official minimization of the U.S. action, officials of the new administration concede that they themselves cannot foresee the full implications of what is happening in Zaire.

The Carter administration is engaged presently in overtures toward normalizing relations with Cuba. At the same time, an estimated 12,000 to 15,000 Cuban troops who helped to defeat U.S. supported factions in Angola remain in that country, and Cuban President Fidel Castro is currently visiting Africa. In addition, Soviet President Nikolai Podgorny, whose nation gave massive support to the pro-Marxist victory in Angola, next week visits Tanzania, bordering Zaire, and other African nations, in a new display of Soviet interest in Africa. Castro is due to arrive in Tanzania today.

In response to Zaire's requests for emergency deliveries, U.S. officials said, a chartered DC-8 transport left Dover Air Force Base in Delaware yesterday for Kinshasa, capital of Zaire, the former Belgian congo.

That aircraft was scheduled to deliver to Zaire parachutes, backpacks, communications equipment, medicine, combat food rations and flexible fuel tanks, all worth about $500,000.

A second DC-8 later this week is scheduled to fly from the same base with a slightly larger valued shipment of spare parts for C-130 transport aircraft previously supplied by the United States.

The Pentagon leased both charter flights from Seaboard world Airways, officials said.

"I understand this is the extent of the request" from Zaire "for these two planeloads and beyond that I am not going to speculate," said State De partment spokesman Frederick Z. Brown.

Other sources said Zaire's request was "pared down" to eliminate "lethal equipment." State Department officials said Zaire also has made military aid requests to Western European nations. Brown said "there has been consultation with Congress" on the shipments.

Rep. clarence D. Long (D-Md.), chairman of the House Appropriations Subcommittee on Foreign Operations, however, said yesterday that he was "presented with a fait accompli."

Long, through a spokesman, said he received "a courtesy call" yesterday morning from William E. Schaufele Jr., assistant secretary of state for African affairs, who told him about the airlift for Zaire, with equipment from previously authorized U.S. aid funds.

Long was described as having "very serious reservations" about the decision involving "an internal conflict in Zaire," and said he will take "a very hard look" at aid requests for Zaire in hearings next week.

White House press secretary Jody Powell stressed yesterday that President Carter personally approved the emergency supplies for Zaire and is giving "no thought or consideration to sending ground troops there."

"We're dealing with a friendly country in Africa that is under armed attack from sources not completely clear," Powell said, "and we are dealing with a moderate amount of equipment." Powell added that "we have been for years providing military aid to Zaire. This is certainly not a dramatic departure from what we have been doing. . ."

"We're not sending arms" or ammunition, said Powell: "Were sending batteries and shoes and britches and matters of that nature."

Jerrold Schecter, spokesman for the National Security Council staff, emphasized that the shipment consists of supplies "already in the pipeline" as part of Zaire's $30.2 million in foreign military aid this year. Zare also is currently receiving $12.75 million in economic assistance and $14.9 million in food aid, Powell said.

The United States has been a major supporter of Zaire since that nation, rich in copper and about the size of the United States east of the Mississippi River, gained its independence in 1960 and was plunged into multiple, separatist rebellions. It is the remnants of one rebellious force, the Katanga gendarmes who ultimately found refuge in Angola and fought on the side of the pro-Marxist forces in Angola's 1975-76 civil war, who are now said to be forcibly reentering the former province of Katanga, now known as Shaba, from Angola. In 1975-76 these forces fought western-supported factions, who were aided by $30 million worth of American CIA funds.

State Department spokesman Brown said yesterday, "I can't confirm who it is" who is "invading" Zaire, "and where they are coming from."

Zaire now claims that some 5,000 "mercenaries" have crossed from Angola into Zaire and uses a thinly-disguised euphemism to describe them as Cuban-led. Belgian sources put the Katangan border crossers at only about 500.

Zaire's news agency, Azap, using a triple euphemism, said yesterday that "This group of mercenaries was led by other mercenaries who come from across the Atlantic, and who enjoy the support of third countries that seek ideological conquests." That multiple circumlocution evidently meant Katangese, led by Cubans, supported ny the Soviet Union.

The fighting, first disclosed March 8, has now spread beyond the original Shaba Province towns of Kapanga, Sandoa, Kisenge and Dilolo, U.S. officials said. Zaire claims the troops involved are armed with 122-mm. missiles and long-range rockets of the type "previously used in Angola by the Russo-Cuban coalition" which defeated the Angolan factions supported by Zaire and the United States.

Diplomatic sources in Kinshasa said yesterday that the invasion force has killed about 50 Zairese Army soldiers, and opened up a 60-mile front between Sandoa and Kisenge.

About 15 American missionaries reportedly left Sandoa. The State Department said that about 90 Americans remain in the area, including 82 employees and their family dependents of Constructeur Inga-Shaba.