U.S. and Soviet military leaders met today for the first time since the cold war era began and focused on force reductions in Europe - with American officials concluding that Moscow viewed the problem as a U.S.-Soviet issue and the Americans saving it is a matter that Ultimately must be dealt with by NATO.

American officials considered the meeting an important step in U.S.-Soviet relations, not so much for the proposals discussed, but because the defendse ministers and military chiefs of staff of the world's two greatest powers had finally met and talked.

The defense and military leaders also discussed military problems associated with vertification of SALT, including Carter's decision to employ the MX mobile missile, and the deployment of a Soviet version of the mobile missile.

The decision to hold the meeting was made by President Carter and Soviet President Leonid Brezhnev at their morning meeting at the Soviet Embassy. The military men met for an hour and 40 minutes as the two presidents took their lunch break.

The principal Americans attending were Defense Secretary Harold Brown and Chairman of the Joint Chiefs of Staff Gen. David Jones. Their counterparts were Soviet Defense Minister Dmitri Ustinov and the Soviet military chief of staff, Gen. Nikolai Ogarkov.

While the participants observed the usual conference formalities, one American official said he believed the session was "a good bit more informal" than the Carter and Brezhnev meetings.

Carter had come to Vienna hoping to persuade the Soviets to hold meetings among defense and military officials and the Americans consider it a worthwhile accomplishment to have gotten at least this far.

The Soviets have not been anxious to hold such talks in the past. Malcolm Toon, the U.S. ambassador to Moscow, had tried in vain for two years to meet with Ustinov to invite him to Washington to see Defense Secretary Brown.

According to American officials, when the Soviets discussed troop reductions in Europe, they talked in terms of an arrangement that would be made by the United States and Moscow.

"Our impression was that they were attempting to split us off from the alliance," one U.S. official observed.

When the Soviets discussed the force reduction issue in bilateral terms, he said, the Americans responded that they considered at a matter for the entire NATO alliance. The U.S. team said it could talk about the force reductions with the Soviets, just as any Western Europeans could, but could not be expected to come to any final arrangements.

The Soviet emphassis on making the Europeans reductions a bilateral matter did not surprise the U.S. side, because this has long been the Soviet approach. The negotiations on mutual balanced force reductions have been going on between NATO and the Warsaw Pact since 1973.

The negotiations have focused for the past year on a first phase of U.S. and Soviet reductions proposed by NATO negotiators and the commitments on the numbers and the timing of future reductions. But the negotiations have broken down over the central question of how many troops the Warsaw Pact has in the European theater.

The Americans say Moscow has more troops in Europe than it will admit. One U.S. delegate said: "We know the real numbers - and we believe they know that we know them. But the Soviets have already taken a real firm position on this, and so it is hard for them to change it now."

Recently, Leslie Gelb, the State Department's director of politico-military affairs, has been meeting in Washington with a Woviet Embassy official to find some way of resolving the impasse.

American officials stressed that while nothing was resolved in the military talks, the sessions were considered by the United States to be quite useful. No date was set for a further meeting, an American official said. But he added that as the session adjourned, one of the Soviet officials told the Americans: "Now that we've met, we'll have to meet again."