In the aftermath of the INF Treaty, attention in the West is now sensibly turning to conventional defense and arms control in Europe. After Mikhail Gorbachev's visit to Washington, there is even a hum of optimism in the air on this subject. Such humming should stop. Significant progress in conventional arms control negotiations with the Soviet Union in the next several years is quite unlikely.

It is true that Moscow's rhetoric concerning conventional arms control has changed. In calling for deep reductions of conventional arms, Soviets now routinely use the phrase "reasonable sufficiency" to describe the proper objective of Warsaw Pact and NATO defenses. They call for a transformed European security system based on "new thinking" in which neither alliance has the capacity for surprise attack. They admit that the Warsaw Pact has asymmetric advantages in some conventional weapons systems such as tanks. Moreover, major cutbacks in the Red Army would certainly assist Gorbachev's efforts to reform and reinvigorate the Soviet economy. So why the pessimism?

1. The Warsaw Pact enjoys conventional superiority in Europe with no prospect that NATO will build up its conventional forces. Moscow could well wish through an arms control agreement with the West to codify its conventional advantages at lower levels. Why should it wish to negotiate them away?

2. It is possible that the U.S.S.R. would be willing to trade some armor for Western nuclear weapons and/or dual-capable aircraft. After INF, such a deal would further the Soviet goal of a denuclearized Europe and therefore will for the foreseeable future be unacceptable to NATO. So what Moscow wants, NATO will not give.

3. Withdrawing many Soviet divisions from Eastern Europe could incite unrest there and threaten Gorbachev's hold on power.

4. Any NATO conventional arms control proposal should propose deep cuts in Soviet forces in the western U.S.S.R. as well as major withdrawals of the Red Army from Eastern Europe. James Thomson of the Rand Corp. and I have suggested elsewhere equal tank and artillery limits for NATO and the Warsaw Pact in the Atlantic-to-the-Urals area and in Central Europe and have argued that because of the immense mass of Soviet reinforcement capability from the U.S.S.R., small reductions, even if asymmetrical, would be worse than nothing. But equal armaments ceilings would require the elimination of tens of thousands of Warsaw Pact and especially Soviet tanks and artillery. This would signal not just an arms control agreement but a fundamental transformation of the postwar political order in Europe. Not likely.

5. Verifying a conventional arms control agreement would be enormously difficult and would require rapid Western access to thousands of Eastern military installations as well as the Soviets' willingness to expose, through an exchange of information with the West, their order of battle down to the battalion level. To imagine such military openness -- far beyond the INF verification regime -- is to contemplate another sort of Soviet Union than even the most accommodating Gorbachev could likely deliver.

6. Gorbachev can reduce the size of the bloated Soviet armed forces unilaterally, thus saving money, without appreciably diminishing the military threat to Western Europe. This could include small Soviet troop withdrawals -- no more than four divisions -- from Eastern Europe, which would be meant to impress Western public opinion, stimulate NATO reciprocity, allow rapid reintroduction of Soviet forces in time of East European turbulence and avoid stringent verification. In fact, one could argue that if Gorbachev really wishes urgently to reduce Soviet spending on conventional forces, he cannot afford to wait for a treaty with the West that at best could take years to conclude.

This is not to say that the United States and NATO should give up on this endeavor as hopeless. To do so would both leave the initiative with Moscow and miss the opportunity to test Gorbachev's fine-sounding phrases. Therefore, the alliance needs publicly to put forth soon its concept for conventional arms control in Europe and explain how this concept fits into Western strategy. But to believe that Gorbachev -- no matter how visionary -- through good will and arms control will rescue the West from its conventional inferiority in Europe is to be on the lookout for Santa.

Thus, nuclear deterrence will remain a crucial element in the defense of the West. After the INF Treaty is ratified, we can expect renewed Soviet and Allied, especially German, domestic pressure to reduce, even eliminate, battlefield nuclear weapons in Europe with ranges below 500 kilometers. Foreign Minister Hans-Deitrich Genscher of West Germany has stated that he has a commitment from NATO ministers that the alliance will expeditiously press for follow-on talks with Moscow on these short-range nuclear systems, most of which are deployed in the Federal Republic. Since such a negotiation would serve Moscow's objective of moving toward a nuclear-free Europe, one could expect much more Soviet flexibility here than with respect to conventional forces. Thus NATO's enduring conventional inferiority could be matched by an ever less credible nuclear deterrent. Call it old thinking or new, this is what Moscow may have in mind. Gorbachev can, of course, demonstrate otherwise -- but not on the pages of Pravda.

The writer was U.S. ambassador to the conventional force negotiations in Vienna from 1985 until this year, and is now teaching at Harvard's Kennedy School of Government.