The leaders of NATO, responding to President Carter's concern about Soviet-Cuban involvement in Africa, warned the Soviet Union yesterday that its military actions in the Third World could "jeopardize the further improvement of East-West relations."

But the warning, issued at the end of a North Atlantic Treaty Organization summit meetingthat devoted unprecedented attention to Africa, came against a background of confusion and discomfiture among alliance leaders about how best to deal with the Africa situation.

British Prime Minister James Callaghan, normally Carter's staunchest supports in Western Europe, flashed a go-slow signal at suggestions that the West rush into stepped-up involvement in Africa conflicts.

In reference to the Carter administration's escalating criticism of Moscow and Havana, Callaghan told reporters that he wasn't sure that he heard a clear voice coming out of Washington.

"I hear several voices," he said, "There seem to be a number of Christopher Columbuses setting out from the United States to discover Africa for the first time . . . It's been there a long time."

However, West German Chancellor Helmut Schmidt, who has been Carter's most persistent European critic in the past, told a separate news conference that he could understand "the noise about Africa."

It was important, Schmidt said, for the United States to impress on Moscow that it views Soviet interference in Africa with the utmost seriousness and to make clear that continued Soviet drives for global power could have a domestic U.S. impact making it difficult for Carter to win Senate approval of a strategic arms limitation talks (SALT) agreement.

In the end, the NATO leaders bridged their differences over how to approach the African situation by including a general expression of concern in their final communique.

Although it didn't mention Africa specifically, the communique noted "the repeated instances in which the Soviet Union and some of its allies have exploited situations of instability and regional conflict in the developing world."

It added: "Disregard for the indivisibility of detents cannot but jeopardize the further improvement of East-West relations."

On the military front, the communique said that the NATO allies "will continue to devote all the resources necessary to modernize and strengthen their own forces to the extent required for deterrence and defense."

Carter, in a separate statement issued yesterday, underlined in his strongest words four-square behind the that he stands for-square behind the longstanding U.S. policy that equates a Soviet attack on Europe with an attack on the United States.

"An attack on Europe would have the full consequences of an attack on the United States," the president said.

"Let there be no misunderstanding: the United States is prepared to use all the forces necessary for the defense of the NATO area." The word "all" was underlined in the Carter text handed out to the press.

Carter, in focusing on the nonnuclear forces, hailed the Long Term Defense Program calling for allicance-wide development and production of weapons as a way for NATO to get more bang for the buck.

However, despite the attempts to focus attention on the military decisions taken during the meeting, Africa was clearly the subject that dominated the behind-the-scenes discussions and the press attention to the summit.

Reliable sources said that a rough breakdown of the attitudes expressed by different members would put the United States, together with West Germany, France and Belgium, into a camp advocating some kind of active western counter-action to the Soviets and Cubans in Africa.

On the other side, the sources continued, Britain and some of the smaller countries, most notably the Netherlands, Norway and Denmark, took a more cautious approach. In particular, these countries are known to be concerned that any actions by NATO countries in Africa not bear the official imprint of the alliance.

That question was addressed by NATO Secretary General Joseph Luns at a closing news conference.Asked about upcoming meetings in Paris and Brussels, at which the United States and some other members will discuss possible creation of some kind of peacekeeping force for African conflicts, Luns said:

"My feeling is that any European force in Africa will not be realized. All our allies agree that NATO as such should not get involved in Africa."

In regard to other political questions that have been troubling the alliance, the final communique glossed over the dispute between Greece and Turkey over Cyprus and differences about the Middle East.

The communique made a veiled appeal to the U.S. Congress to lift the arms embargo imposed against Turkey for its 1974 invasion of Cyprus by expressing hope "that full cooperation among members in all aspects of the defense field will be resumed."

The oblique wording of that appeal was described by reliable sources as a concession to Greek Prime Minister Constantine Karamanlis, who objected to any language that would have called explicitly for repealing the embargo.

The sources said that, after strenuous behind-the-scenes protests by Israel, the communique deleted a planned reference to the need for basing a Middle East peace on U.S. Resolution 242. That resolution says Israel must withdraw from occupied Arab territories.

Defense Secretary Harold Brown, in winding up the two-day NATO summit meeting, said its "centerpiece" was the allies' endorsement of the Long Term Defense Program.

He warned that, although the endorsement of the paper blueprint was a big forward, the NATO officials must follow through with it back home or "we'll lose momentum and have to climb the same hill all over again."

The rough estimate of the cost of implementing NATO-wide development and production of weapons from calender 1979 through 1983 is between $60 billion and $80 billion, with the United States contributing "a little over half of that total," according to a U.S. defense official who briefed reporters yesterday.

Under the planned annual increases of 3 percent in defense spending by most of the NATO countries, the official said, "the bulk" of the long-range program would be covered. "It isn't a big add on," he said.

Although the NATO allies agreed to cooperate on projects ranging from the design of the next generation of antitank weapons to a plan for bringing reinforcements and supplies from rear areas to the front lines, there are several issues to be resolved.

One of these concerns beefing up the reserve forces of European allies. The United States' recommendations in this regard, said the defense official, were not greeted with enthusiasm.

Brown said if the United States refused to buy weapons abroad, as envisioned in the master plan, the Europeans might well turn that into a losing proposition for this country by building their own.

NATO discussions and official papers touched only lightly on modern tactical nuclear weapons, including the neutron warhead. "Measures are being developed to ensure that NATO's theater nuclear forces continue to play their essential role in NATO's deterrence and defense posture," said the official paper on the Long Term Defense Plan.