A key issue as the United States and the Soviet Union open talks about European nuclear arms control Nov. 30 is the current East-West balance - or imbalance.
The Soviet Union claims that a balance in European medium-range nuclear weapons exists now, and that any arms control must therefore reduce weapons equally on both sides. The West claims that the Soviet Union has a lopsided superiority in ''Eurostrategic'' weapons, and that any arms control must therefore reduce Soviet weapons more than Western ones to achieve equality.
This difference is crucial, for Western figures give the Soviet Union a 2-to- 1 advantage over NATO in this category of weapons - and an even greater advantage in the number of actual warheads (bombs or equivalents).
Normally, such a dispute would be resolved by experts. The general public would get involved only on conclusion of a treaty, and then only to nod or shake its collective head as the treaty came up for ratification.
This time around it's different. Because of strong popular Western European opposition to NATO nuclear missiles planned for deployment beginning two years from now, the existing numbers have already become a public issue.
If Moscow persuades the public that the planned missiles are a Western attempt to upset a present balance and acquire superiority, then public opinion could force the European governments to abandon the new weapons. If Washington and the NATO governments persuade the public that there is now a glaring imbalance, they could go ahead with deployments - or else their determination to do so could force Moscow to agree to arms reductions.
Both Moscow and Washington are therefore courting European public opinion.
So far, Moscow appears to be winning, even though it would seem to have a weaker case from raw figures. Many of the antinuclear protesters accept Moscow's assertion of a rough 1,000-to-1,000 parity uncritically. And most European newspapers and magazines (with a few exceptions like The Economist and Die Zeit) seem to settle for general unquantified assumptions about the balance, to think that numbers don't matter anyway, or to take a neutral Moscow-says-this-Washington-says-that approach.
So far, Washington has not helped its own case in Europe very much, largely because old habits die hard, and the Pentagon's natural instinct is to paint the adversary as black as possible. Instead of presenting clinical comparative statistics, the US government has cried ''wolf'' about every conceivable Soviet weapons program, whether starkly threatening or mildly reassuring. It has generally failed - as in a booklet published by the Defense Department this fall charting the Soviet military buildup - to give sober comparisons with American or Western programs or countermeasures.
Such a cheerleading campaign may fire up patriotic voters in Middletown. But it induces undiscriminating cynicism about every American claim among Europeans who are again seized with angst about nuclear annihilation.
The Soviet Union has not been any more clinical than the US in presenting military statistics. On the contrary, it classifies all military figures and until a few weeks ago presented no statistics at all on the European nuclear balance other than the rule-of-thumb 1,000 vs. 1,000.
Since the man in the street tends to assume that a rough balance exists until he is shown evidence to the contrary, however, the burden of proof of an imbalance has rested on Washington. And this burden has been rendered even more difficult by the residue of public suspicion following revelations of past American duplicity such as that during the Vietnam war, when US officials were less than candid about US bombing of Cambodia, and the more recent hiding of ''neutron bomb'' research appropriations in the energy budget.
At this point a new stage in the assessment of the European nuclear balance has opened with the publication of more specific Soviet figures for this balance. In a written interview published in Der Spiegel in November Soviet leader Leonid I. Brezhnev offered precise Soviet statistics: 986 NATO long-range nuclear weapons capable of striking the Soviet Union vs. 975 comparable Soviet weapons capable of striking Western Europe.
It is not clear just how Mr. Brezhnev arrived at these figures. He did not give an itemized breakdown, and the Soviet press attache in Bonn could not provide this breakdown either. Updated statistics from London's International Institute of Strategic Studies (the most generally accepted public military figures) would give a very different balance for the same categories of weapons covered by Brezhnev: 792 (NATO) vs. 1,639 (Soviet Union) if 720-kilometer-range weapons are excluded, or 972 (NATO) vs. 2,139 (Soviet Union) if they are included.
What Brezhnev did say was that his figures covered European nuclear weapons of a range of more than 1,000 km. (He then specifically included American F-4s, however, which are listed by the IISS as having a range of only 750 km.And he may have included NATO's Pershing 1A missiles, even though their range of 720 km. means they cannot reach the Soviet Union from their bases in West Germany; this point is especially unclear, since their inclusion would produce a number much higher than Brezhnev's 986, and their exclusion would produce a number much lower.) Brezhnev specified that his total included 64 British and 98 French submarine and land-based launchers, plus 55 British and 46 French bombers, for a British and French subtotal of 263 systems and, by subtraction, 723 American systems.
Brezhnev listed American weapons included as the F-lll, the FB-lll, the F-4, and planes based on aircraft carriers (presumably the A-6 and A-7). The IISS discounts the FB-lll altogether, claiming it is not a European theater weapon since it is based in the US. The IISS total for all the other American weapons comes only to 540, well short of the Soviet figure of 723. (The Economist would further reduce this figure to 433, since both the IISS and the Brezhnev statistics count planes from a second American carrier that has not actually been stationed in the Mediterranean for the past two years, and both the IISS and the Brezhnev statistics also count 80 F-4s that are actually based in the US not Europe.)
The breakdown of Soviet figures for Soviet weapons is equally unclear. Brezhnev indicated that he was including the SS-20, SS-4, and SS-5 missiles; these would add up to 555 in the Economist update of IISS figures. Brezhnev presumably also included the Soviet Backfire, Badger, and Blinder bombers (500 in number, according to both the IISS and the Economist). The IISS-Economist overall totals for Soviet systems would thus be 1,055, rather than the Soviet figure of 975.
If the Soviet Union in fact counts as European weapons only those SS-20s stationed west of the Urals - and not those stationed east of the Urals but capable of swing-targeting either Europe or China - the itemized tally of Soviet-counted Soviet weapons would be 967, closer to Brezhnev's figure. This still omits, however, the 39 Soviet nonstrategic G-class SS-N-5 submarine launchers, bringing Soviet total to 1,006.
A further bit of legerdemain is involved, for to be fair either all the Soviet systems that are the equivalent of the NATO systems counted by Brezhnev should be included - adding the 480 1,600-km.-range Fencer fighter bombers and, if the 720-km. Pershing 1A is included, the 500 720-km. Flogger fighter bombers - or else equivalent systems would have to be excluded from both sides, leaving out all fighter bombers (i.e., the Soviet Fencer and Flogger, and the American F-4, A-6, and A-7).
Rejecting either choice, the Soviet Union says that all US ''forward-based systems'' (planes based on European land or waters that are capable of hitting the Soviet Union) must be counted in the European nuclear balance, while Soviet planes capable of hitting the European bases of the American planes must be excluded.
An even fairer account of the ''Eurostrategic'' balance would have to separate missiles - which can reach their targets in minutes if they are ballistic missiles and have a superior ability to penetrate defenses - from slow-moving and highly vulnerable airplanes. This subtotal would give NATO only 162 British and French (and no American nonstrategic) missiles capable of striking the Soviet Union as against 1,639 Soviet nonstrategic missiles capable of striking NATO targets.
A still fairer balance would have to pit warheads against warheads (for example, each Soviet SS-20 has three warheads, while each American bomber has two warheads). This analysis puts the score at NATO, 746, and the Soviet Union, 1,653, if 720-km.-range systems are excluded.
A still fairer balance would incorporate quality as well as quantity, including such things as age, survivability, reliability, and penetration. This creates an updated IISS total of NATO, 148, the Soviet Union, 609 ''arriving warheads.''
This still leaves out such factors as accuracy (which currently favors the Soviet SS-20 but will favor NATO's Pershing II once it is deployed); rapid missile reload capability (which favors the SS-20); rapid aircraft reinforcement (which favors the Soviet Union because of geography); and shorter-range (though nonbattlefield) nuclear weapons (which favor the Soviet Union, since SS-21s and SS-22s and soon SS-23s deployed in East Germany can hit prime NATO targets in West Germany, while comparable-range NATO weapons cannot hit the Soviet Union).