Apparently satisfied that President Carter's handling of the Cuba dispute has defused a potential U.S.-Soviet crisis, soviet leaders are moving on to arms control in Europe as the next superpower test of will and intentions.

In interviews given on the condition that they not be identified senior Kremlin officials this week expressed both praise of Carter's Oct. 1, speech on Cuba and dismay about the initial American skepticism toward Leonid Brezhnev's disclosure Saturday of Soviet troop cuts in East Germany and his proposals to reduce nuclear arsenals in Central Europe.

These highly authoritative sources described Brezhnev's speech as "practically an invitation to the United States to begin cooperation for Salt III before the formal negotiations start."

While announcing a 12-month reduction of up to 20,000 Soviet troops and 1,000 tanks in East Germany, Brezhnev offered several ideas to cut back both sides' nuclear-tipped missile forces and begin the next round of strategic arms limtation talks "immediately after entry into force of the Salt II treaty."

At the same time, he warned anew that in the Soviet view, a U.S. plan to deploy new nuclear-tipped Pershing and Cruise missiles in Western Europe targeted on the Soviet Union would "upset the balance of forces that has taken shape in Europe", bringing certain Soviet response.

A high-level NATO study group supports the plan as redress of Western weakness in the face of what it says is substantial Warsaw Pact and Soviet military superiority in Central Europe. NATO defense ministers are likely to approve the plan at a mid-December meeting, and Soviet moves and statements on the issue must be seen in that light.

That senior Soviet officials here, who seldom speak to Westerners, would feel it necessary to amplify and expand on their leader's East Berlin speech so quickly underscores the Kremlin perception of the high stakes Moscow and Washington now are playing for in Europe and the state of tension that exists between the two capitols in the aftermath of the crisis over Soviet troops in Cuba. That crisis left the SALT II tready in doubt of ratification by the U. S. Senate.

Brezhnev said the Soviets back a start of the next round of strategic arms limitation talks "immediately after entry into force of the SALT II treaty." But the treaty is still hostage to the controversy over the Soviet troops and Carter's countermeasures, which include beefed-up American military strength in the Caribbean as an alternative to his unsuccessful effort to get the Soviets to withdraw the units.

Just before Carter's Oct. 1 address announcing his moves. Central Committee American specialist Georgi Arbatov in an interview said it was up to the administration to show "enough wisdom and statesmanship" to defuse the issue and free the treaty for Senate ratification.

Soviet propaganda has since denounced Carter's handling of the crisis as "gunboat diplomacy," but senior Soviet sources said privately they regard the president's speech, in the words of one, "the most courageous" of his term because he skirted direct confrontation with the Soviets over what the Kremlin has always termed a "fabricated issue."

This private praise may be reflected publicly in the fact that the Soviets have been relatively restrained in their handling of the troop controversy. It is unthinkable that the Soviets would publicly approve of Carter's moves, since this would anger Fidel Castro and tend to weaken the Soviet position that the outcome could not have been any different.

If the Soviets feel more confident than two weeks ago that they can do business with Carter, there is little public sign of it detectable here. Indeed, there is clear evidence that Moscow is probing to exploit whatever similar doubts the administration's sagacity may exist in Western Europe.

For example, the party daily Pravda in a commentary today asserted that "the plans of the transatlantic militarists are in irreconcilable conflict with the vital interests of the people of the whole of Europe.These doom-laden plans can be foiled and must be foiled."

A similar campaign was waged by Moscow two years ago against the enhanced radiation weapon, the so-called neutron bomb. There was genuine apprehension over the device in Europe and Carter last April decided against warhead production. This Soviet attack against the medium-range guided missile scheme is similar in many respects, but the time to a decision much shorter.

The senior Soviet sources say Brezhnev's East Berlin speech represents a bold new move by the aging leader to break the long deadlock over East-West force reductions in Europe. If the Soviets indeed sought to open a full, continent-wide debate on the issue, it is unclear why the leadership waited so long to make its move in view of the NATO decision scheduled in two months. This is hardly time enough for a serious public exploration of the questions. The sources suggest one reason the Brezhnev speech was not made earlier may be that he made the proposals against strong opposing advice within some parts of the ruling circle.

Among other things, Brezhnev said the Soviet Union is prepared to reduce its present number of medium-range missiles now deployed in European Russia if no additional similar missiles are deployed in the West.

At least three fascinating theories are being drawn from this proposal:

The Soviets are so worried about the NATO plan they are willing to reduce their own protection to prevent the Pershing-Cruise deployment;

The Soviet missiles in question are outdated, unreliable, and removal would have effect on the Russian arsenal;

The Soviets have far more missiles than they need for strictly defensive purposes.

In any event, it is plausible to believe that no military chief would easily back such a proposal, however devoid of meaning it may in fact have been. So Brezhnev and his supporters may indeed have had a struggle of some sort behind the scenes to include the proposal in the speech.

Which their leader having taken what the authoritative sources describes as a softer line than some advised, they now say the cool reception by the United States has brought new Kremlin apprehensions about U.S. intentions.

"We are in a critical moment," asserted one authoritative source in an exchange clearly intended for Washington. "On the one hand there are some debates on SALT II and some difficulty with ratification. On the other, this special, even critical moment is closely connected with the necessity to create, as a preclude to SALT III, a constructive atmosphere.

"It is connected with the proper direction of all actions which both governments could take today with respect to SALT III negotiations. On our efforts depends making SALT III negotiations more quick, more effective and at the same time, it is very important because it could create the situation which could prevent a new round of the arms race in Europe and not only (there)."

This source added, "That is why we propose in a very decisive way, taking into consideration the lack of time to work together, that we consider this problem with all the responsibility which is the result of the present [urgent] situation."