Former secretary of state Henry Kissinger gave today what might be the first concrete signals that the incoming Reagan administration intends to change U.S. policy toward Africa by viewing it more as an area of confrontation with the Soviet Union.

"It is not tolerable that the Soviet Union and its proxy forces engage in expansion all over Africa and in the Middle East without opposition," Kissinger told reporters after returning to Cairo from Somalia, where he took a one-day break in his Middle East trip.

Although Kissinger has described the tour as private, he has spoken out extensively about U.S. foreign policy -- past, present and future -- and the trip has had the impact in the region of an officail mission for the incoming Reagan administration. Kissinger has said that while he would take on specific tasks for the administration, he forsees no formal role in it.

"I think the Reagan administration believes in a balance of power and bleieves that expansionism must be checked," Kissinger said.

He added that Somalia was "threatened" by neighboring Ethiopia, which is supported by about 13,000 Cuban troops and about $1.5 million worth of Soviet arms.

For the most part, the Carter administration has sought to deal with the continent outside the sphere of East-West confrontation and more in terms of African concerns, particularly about white rule in southern Africa. Promoted intitially by Andrew Young, former ambassoador to the United Nations, the policy reaped better relations with many African nations that discerned a shift from Kissinger's more global approach.

Kissinger's remarks in support of Somalia, reported by news agencies in Cairo, were far stronger than any made by the Carter administration, which has tried to leave open the door for friendship with Ehiopia -- a U.S. ally until the 1974 overthrow of emperor Haile Selassie in a Marxist military coup.

Somali officials interviewed in Mogadishu recently warned of the Soviet-Ethiopian threat to their county and were obviously seeking the kind of backing Kissinger gave them today.

Kissinger met yesterday in Mogadishu with Somali President Mohammed Siad Barre. In an interview with NBC television after the talks, Siad Barre criticized President Carter and expressed hope that Presiden-elect Ronald Reagan would be more forceful.

Complaining about the lack of U.S. military aid, the Somali leader said that "had Carter's steps been more prompt, a stable atmosphere would have been attained in the region." Kissinger said before leaving Mogadishu that he advocated an increased U.S. military preence in the Indian Ocean area.

Escalation of American military assistance to Mogadishu could embroil the United States in a long-simmering feud between Ethiopia and Somalia over the Ogaden territory in southeastern Ethiopia.

Twice in the last two decades there has been full-scasle warfare and last summer Ethiopian farces inflicted heavy losses on Somalia troops and guerillas of the Western Somali Liberation Front fighting to control the area. Ethiopia has regained control ofmost of the territoy and its troops on occasion have crossed into Somalia.

Any U.S. involvement could lead to a deterioration of relations with many African countries. Somalia has not received any African support for its territorial claims and several nations have criticized it for violating a cardinal African principle that the boundries left by colonialism, although far from ideal, must be respected to avoid endless border wars.

The Carter administration vaciliated for three years about whether to ally itself with Somalia after the Soviet Union dropped Somalia in 1977 and gave military aid to Ethiopia.

Washington finally signed an agreement last August with Samolia to provide $40 million in weapons in return for the use of Somali air bases and ports for the U.S. Rapid Development Force being used to bolster the American military presence in the Indain Ocean following the 1979 Soviet invasion of Afghanistan.

Congress, however, has prevented delivery of the arms, since it stipulated that no weapons should be delivered until the government can provide "verified assurance" that there are no Somali troops in the Ogaden.

U.S. diplomats in the Horn of Africa make it clear the believe there are still Somali troops in the desert area, about the size of New Mexico, despite Somali claims that only guerillas of the Mogadishu-backed liberation front are fighting the Ethiopians there.

The arms barrier could be lifted, however, by the new Congress, particularly since one of the key opponents of arming Somalia, Rep. Stephen Sonaz (D-N.Y.), is giving up his chairmanship of the House foreign affairs subcommittee on Africa in favor of that on East Asia.

Kissinger imlpicitly criticized the congressional action when he was asked in Cairo about chances of expanding U.S.-Somali military cooperation:

"Let us first implement what already had been signed and then one can see about expansion. This is a matter I would like to report to the leading personalities of the Reagan administration who will have to make the decision."

He described Somalia as "a country that is threatened by a heavily armed neighbor in which there is much Soviet equipment, Soviet proxy forces of Cubans, other communist-supported forces from East Germany and South Yemen. And it is a country that is located stategically at the mouth of the Indian Ocean and of the Red Sea."

"This a matter that, in my personal judgement, cannot be of indifference to the United States," he said, adding, "Our friends will become dubious."

In recent months Ethiopia has succeeded in isolating Somalia dipolomatically by gaining support on the territorial issue from Neighboring Kenya and Sudan, two former recipents of U.S. aid in Africa.

Kissinger paid little attention to Africa during most of his years of foreign policy leadership under the Nixon and Ford administrations. The influx of almost 20,000 Cuban troops into newly independent Angola in 1975-76, however, turned his attention to southern Africa, where he unsuccessfully sought to bring about a negotiated settlement of the Rhodesian war.

A critic skeptical about this sudden attention to the continent, said, "Kissinger is the only person who ever discovered Africa through Cuba."