While world attention is focused on US-Soviet nuclear arms talks in Geneva, interest is quietly heating up in negotiations to reduce conventional forces in Central Europe. There is a growing feeling that advances in arms control could come sooner in this category than in intermediate and strategic nuclear weapons.
Discussions on mutual and balanced force reductions (MBFR) have been going on in Vienna for nearly 10 years between NATO and the Warsaw Pact. But recent participants in the talks, as well as close observers, see new concern and activity on MBFR at the State Department, Pentagon, and within the NATO alliance.
''It's been kept fairly hush-hush so far, but I do know that something is going on,'' said one US government source. ''I know that at the moment there is specific allied and US diplomatic activity in this area, that they are exploring and looking for ways to move.''
''There is movement afoot in the alliance on this issue,'' said another American recently returned from a classified intelligence project in Europe.
Close observers see a coincidence of events that points toward possible progress on slowing the steady buildup of conventional forces in Europe:
* The Soviet Union is eager to reach an agreement on military confidence-building measures (such as more notification of troop maneuvers) through East-West talks under way in Madrid. Such measures could relate directly to MBFR. A proposal at Madrid (where follow-up discussions to the Helsinki Final Act on European cooperation, human rights, and security are being held) includes new East-West meetings on disarmament and how to prevent surprise attacks. Under the proposal, the meetings would begin next fall in Stockholm.
* The British and French are emphasizing strategic nuclear forces in their defense buildups and would welcome a chance to hold down conventional force increases sought within NATO. It is generally accepted that, for political and economic reasons, most alliance countries other than the United States won't meet the goal of the NATO commander, Gen. Bernard Rogers, which is 4 percent annual defense increases, which are designed to reduce reliance on nuclear weapons.
* West German Chancellor Helmut Kohl, despite denials in Washington, is acting as a go-between for a possible meeting of President Reagan and Soviet leader Yuri Andropov. An agreement on confidence-building measures and limits on conventional forces could be a reason for the superpower leaders to meet, it is suggested here.
* NATO defense ministers meeting in Brussels this week discussed troop levels and deployment. The US would like to be able to focus more of its military manpower on other world trouble spots.
* There is growing awareness that NATO's doctrine of ''flexible response,'' which does not rule out the use of nuclear as well as conventional weapons, should be accompanied by arms control efforts at both levels.
''The devil is in the details,'' says the former US MBFR deputy representative, Thomas Hirschfeld, of the challenges that remain in reaching an agreement with the Warsaw Pact. But the major sticking points at Vienna could be resolved, concludes a new Congressional Research Service report written by a former CIA analyst and early MBFR participant. Congressional researcher Stanley Sloan notes that both sides have drawn closer in their MBFR positions over the years, and that ''there are a lot of factors that make MBFR more relevant today.''
As recently as February, the Warsaw Pact offered a ''goodwill'' withdrawal of 20,000 Soviet troops in exchange for a reduction in American forces in Europe of 13,000. But the West dismissed that as propaganda designed to stir European public opinion regarding the planned deployment of nuclear Pershing II and cruise missiles by NATO.
NATO and Warsaw Pact participants at the Vienna talks have agreed that both sides should reduce total ground and air force manpower to 900,000, with a ceiling of 700,000 for ground forces. The East says there is relative parity. The West says the Warsaw Pact advantage is about 160,000 (including 80,000 Polish forces that the Warsaw Pact says are not combat troops and 50,000 Soviet troops, the equivalent of four divisions). The West wants an agreement on current numbers before any reductions are settled on.
Mr. Sloan says this problem could be bypassed by having both sides provide detailed lists and levels of units to be included within the 700,000 ceiling.
The West wants more permanent and frequent inspection measures to ensure compliance than do the Eastern-bloc countries. Sloan says the Warsaw Pact ''has moved significantly away from its earlier resistance'' to such cooperative measures, and that the West could safely afford to be more flexible in its demands.
The current NATO force reduction proposal focuses on manpower only, while the Warsaw Pact wants to include armaments. Sloan agrees that weapons reductions could harm the West, since the Soviet Union could more quickly reinforce its troops in time of crisis than could NATO. Western strategy currently relies on reinforcement equipment to be pre-positioned in Europe rather than air- and sea-lifted from the US.
Other experts say the West is foolish to concentrate on manpower, since the real Soviet and Warsaw Pact advantage lies in armaments.
''Manpower is a very poor indicator of the military balance,'' argues Phillip Karber, vice-president for national security programs with The BDM Corporation, a Washington-area think tank. ''I would shake in my boots if the Soviets suddenly said, 'We agree with your manpower figures, let's have an agreement.' ''