Leslie H. Gelb, a former Carter SALT negotiator and New York Times reporter, got back from Moscow recently and said he did not doubt that Soviet officials are in the middle of a slugfest over how to deal with the United States. Listening to them discuss their Afghan adventure, he said, he could have closed his eyes and believed he was back in the Pentagon listening to a debate about Vietnam. "While some officials may see opportunity there, others know it is a trap."

I would like to be persuaded. It would give some comfort just to know that Soviet officials have genuine doubts about the invasion of Afghanistan and particularly about the invasion's harmful fallout on relations with the United States. To imagine that those doubts could actually produce what the American debate over Vietnam produced -- a policy reversal -- would be positively uplifting.

But more evidence is needed, I think, than the fact that the few sophisticated Soviets to whom visiting Americans are routinely funneled, and some others, may describe Soviet policy-making in terms familiar to students and practitioners of American policy.

There may well be a canvassing of options, a weighing of costs and benefits and even sharp debate in the policy-forming stage. The face of consensus that the Kremlin likes to show in regard to major decisions can often be a facade. But what is known about Brezhnev-era collective leadership does not prepare me to believe that so soon after a major decision policy-level or policy-savvy Soviet officials would be broadcastng their misgivings and moaning that the costs are too high -- even if they were surprised by the vigor of the American reaction.

More likely to me is that Soviet spokesmen would like to dull American alarm and outrage by invoking a policy-making model with which Americans will feel at ease and by turning American attention to their "problems" and "dilemmas." They want the pluses of their power play but not the minuses. They want Afghanistan -- and SALT, too.

When Moscow invaded, it knew that SALT was already in trouble and that it would be in more trouble after the invasion, but it still invaded. This was a stark choice of provocative empire-building over preventive accommodation, and the implications of it are disagreeable to people who prize SALT and sanity. But there they are.

Even with the invasion, I would agree with GELB that the treaty stands on its own feet. SALT may even be more potentially useful: to make the inevitably more intense Soviet-American political competition safer and perhaps less costly. But competition unquestinably will be more intense, and Afghanistan did it. Things were rough but manageable, more or less, until then. Afghanistan was no action-reaction phenomenon, nor a matter of chicken and egg. It was gratuitous, irresponsible. The Kremlin got greedy. Its professions now of a sharper fear of American designs are difficult to credit.

I doubt that there is any Soviet citizen, except one who is inviting a term in the gulag, who will say seriously that for the Soviet Union Afghanistan is a trap. That is too profound and too dangerous a critique. Yes, there are unpleasantnesses and difficulties. But these are bearable, and will be borne. The Afghans' resistance, the Islamic world's protests, Europe's stutters, American sanctions: all this will be endured. Domestic opposition is zero.

Such debate as there is in the Kremlin would appear to me to be merely about ways to minimize the damages and to test the possibilities of exploiting Moscow's new power position.

Soviet officials profess to see an analogy with Vietnam: just as the Soviet Union pressed North Vietnam to slow its war in South Vietnam and thus made possible the early measures of detente, so now the United States should press the Afghan guerrillas to slow their war against the Babrak regime and thus make possible the later measures. Such, in Soviet eyes, are the responsibilities of a mature great power.

The symmetry is appealing but finally unacceptable. As is clearer to a lot more Americans now than then, North Vietnam was invading another country. The Afghan guerrillas are trying to reclaim their country from a foreign army. It does not work to compare the Nixon effort to induce the Soviets to reduce -- somewhat, for a while -- their backing for an aggressor client, with the Brezhnev effort to induce the Americans to do what they can to see that a victim of Soviet aggression stops struggling.

Detente has a certain meaning if it involves a degree of Soviet restraint in supporting aggression. It has a different meaning if it involves American restraint in resisting agression. That is the distinction that the Soviets are trying to fudge.