Vienna — Is Soviet counterdeployment in response to the siting of new NATO nuclear missiles in Western Europe to be extended to the Balkans? The question came to the foreground after the Soviet Union said last week it will accelerate the deployment of its missiles in East Germany and Czechoslovakia, and warned that other states may also receive them.
The possibility has already been openly posed in Yugoslavia, the Balkan state where concern at such a development would run highest. Even in Bulgaria, one of the Soviet Union's closest allies and the one most likely to be involved in any further upgrading of Soviet and Warsaw Pact nuclear capabilities in Europe, the question has received wide attention.
A meeting of Warsaw Pact defense ministers, scheduled to be held in the Bulgarian capital of Sofia within the next two weeks, may offer the first clue to what further moves the Soviet leadership has in mind. Inevitably, the Balkans and the east Mediterranean - where Greece and Turkey are involved in defense arrangements (including nuclear systems and bases) with both NATO and the United States and Britain (Cyprus) - would be a major issue at such a meeting.
The pact's foreign ministers met in Sofia in mid-October. In it, they repeated Soviet calls for a freeze on the production of nuclear weapons and for nuclear-free zones in Europe.
Yugoslavia and Turkey have never been interested in such a plan, or in Romania's calls for a territorial ban on nuclear weapons facilities, indigenous and foreign, and for removal of military bases.
Greece under Andreas Papandreou has come around to support Romania's proposal. Only a few weeks ago he and Bulgarian President Todor Zhivkov met and expressed ''confidence'' that Bulgaria was not going to be involved in Soviet counterdeployment.
But everything that has happened since the West German parliament's approval of NATO weapons a week ago seems to have placed such ''confidence'' in question. It has also put on hold, for the foreseeable future at least, any hopes for a nuclear-free zone in the Balkans.
The Soviets may be irritated by Romania's almost unilateralist and immediate call to them over the weekend to ''reconsider'' counterdeployment. But given its record of opposition to Soviet foreign policy, the Soviets would not have been counting on their cooperation.
There are no Soviet troops in Romania and Bulgaria. It was rumored last year that missile launchers were then being placed in Bulgaria. There was never any confirmation. But the Soviet warning of more countermeasures revives the option this as an obvious option. The Bulgarians themselves seem uneasy about it.
Poland, East Germany, Hungary, and Czechoslovakia have a full-blown Soviet military presence, and their armies are equipped with Soviet tactical nuclear weapons. Now East German and Czechoslovak capability is being beefed up with Soviet short- to medium-range rockets as a reply to the Pershing IIs and cruise missiles.
In this new impasse in East-West relations, the Soviet Union is certainly pondering the continued nuclear ''immunity'' of the allies on its Balkan flank. Both geography and political dependability suggest it will be Bulgaria (not an ''unreliable'' Romania) that will figure in whatever is agreed in the next week or so.