In his talks with Leonid Brezhnev this weekend, President Carter will seek to expand regular top level U.S.-Soviet contacts to include for the first time meetings between American and Soviet defense ministers and military chiefs.

U.S. officials hope that such talks will begin here as part of an effort to initiate direct communication between the two establishments with the most direct involvement in arms control issues.

The traditionally secretive Soviet defense establishment is believed to have greater influence on Moscow military policies than does the Pentagon on the American government.

U.S. officials said the Soviets have not yet agreed to the specifics of the Carter proposal, but there is hope that contacts could begin on the issue of the new American MX missile.

Administration officials envision that the U.S. military officials could explain to their Soviet Counterparts how the basing of the new missile, would be verifiable by the Soviets - and their view that any planned Soviet mobile missile must be verifiable by the United States, if SALT is to succeed.

The proposal for talks with Soviet military officials is a seemingly modest goal, in a summit at which limited expectations is the official line. Yet U.S. officials regard it as important - especially in view of Brezhnev's failing health. The Soviet military functions with relative independence, and its current leadership is expected to survive regardless of who eventually succeeds Brezhnev.

Moreover, Carter aides feel that regular talks between top U.S. and Soviet military officials would be an important step toward eliminating incorrect impressions that they concede have occured between Washington and Moscow during Carter's first 2 1/2 year as president.

American officials feel the Carter administration has at times sent conflicting signals to Moscow concerning just how it intends to deal with Soviet actions around the world. There have been occasions when some officials, including Secretary of State Cyrus Vance, have stressed cooperation, while others, including presidential adviser Zbigniew Brzezinski have stressed a tougher line against Soviet expansion. Regular summit meetings and ministerial meetings involving defense and military heads could go a long way toward assuring that the two countries understands each other.

This remains one of Carter's goals at the summit, one official stressed, and it is what the president meant when he said in his departure statement: "We will try to broaden our communications with the Soviet Leadership and create new channels of understanding for the future."

So far, the Soviets have been in no hurry to broaden the range of U.S.-Soviet dealings to include conferences between defense and military officials.

For more than two years, the American ambassador in Moscow, Malcolm Toon, has been trying to extend an invitation to Soviet Defense Minister Dmitri Ustinov to visit Defense Secretary Harold Brown. But Toon has never even seen Ustinov, let alone invited him to the United States.

This is one reason administration officials have been placing unusual emphasis, in talks with reporters, on the fact that Brezhnev is bringing Ustinov and the chief of the Soviet military general staff, Marshall Nikolai Ogarkov, who is Moscow's counterpart to Gen. David Jones, chairman of the U.S. Joint Chiefs of Staff.

Carter had told Moscow that he was bringing Brown and Jones with him to Vienna, and urged that their Soviet counterparts be here also.

Because of Brezhnev's weakened physical condition, U.S. officials hope that the sessions Saturday and Sunday will rely on the "collective" leadership of the two sides And they have a scenario for how the separate military talks might come to pass:

American officials do not intend to initiate the discussion of the MX mobile missile. But they do expect to initiate some general discussion to the question of verifiability of missile basings. At this point, they believe the Soviets might register concern, already stated in the Soviet news agency Tass, that the U.S MX missile cannot be adequately verified.

It is here that the U.S. defense secretary and chairman of the joint chiefs will be called on. And bearing in mind the fragile state of Brezhnev's health, and the very limited amount of time for each session, the American cans expects to suggest that perhaps separate military and defense talks can be held at this summit to go into detail on the missile questions.

Whether the separate military talks will occur, however, is uncertain. One Soviet official said that he doubts they will occur, despite the U.S. efforts. Soviet Ambassador Anatoliy Dobrynin, interviewed en route to Vienna, said only "It is possible. Nothing is set."

U.S. officials feel that it would be important to at least establish a pattern in which the American and the Soviet defense and military chiefs would confer.

The Carter officials believe there is a precedent. In the 1967 Glassboro, N.J., summit between President Johnson and Soviet Premier Alexei Kosygin, then-defense secretary Robert McNamara briefed the Soviet officials on how a sharp escalation of strategic arms would develop if both sides developed defensive anti-ballistic missile systems.

At a more technical level, in the actual SALT negotiations in Geneva, U.S. and Soviet military officials have sat together to work out some of technical military problems.

Administration officials believe that the U.S. and Soviet defense chiefs may also wind up working at this summit on the major problem that has been holding up the talks on mutual balanced force reductions in Europe.

The two sides have not been able to agree on just what is the base number of Soviet forces available for military action in the European theater. American officials are seeking what they call a "common definition" of the force levels.

The Soviets have previously proposed a quick reduction in mutual force levels. (Reuter has reported that the Soviets are proposing cuts of 60,000 troops). Yet the United States has contended this is not meaningful without an agreement on the larger issue of just how many troops and which types of weaponry are involved. CAPTION: Map, U.S. Verification System, By Richard Furno - The Washington Post