The moaning and groaning of so many Americans about the fading of our power, our will and what have you seem to have left the Kremlin rather unmoved.

Indeed, the Soviet leadership, far from licking its chops as it contemplates the American turkey going belly up for a gift feast, is showing unmistakable and, I think, healthy signs of alarm at the vigor of the old bird.

What specifically troubles Moscow is that the United States is now playing harder what steady-nerved people like Secretary of Defense Harold Brown have long seen as its high card -- the United States' great technological and industrial potential in defense. Look, for instance, at the latest pronouncement (Pravda, Oct. 25) of Dmitri Ustinov, the Soviet defense minister, n softie, someone who counts.

On the surface, he offers a somewhat but not entirely propagandistic restatement of Leonid Brezhnev's recent demand to NATO not to dare match the Soviet Backfire bombers and SS20 missiles already targeted on Western Europe by deploying there new U.S. missiles capable of reaching Soviet soil.

Underneath, Ustinov quietly catalogs the anxieties the Soviet Union feels as it regards the United States' overall conventional and nuclear modernization plans. These include not just the missiles in Europe but MX, the "quick strike force," etc.

"What has the U.S.A. been driving at recently?" he asks. "Isn't there a danger of their practical moves after the signing of the SALT II treaty producing some serious complications that will put off SALT III and place a burden on Soviet-American relations? This is a natural question, for what we see is an expansion of the aggressive NATO bloc, with the U.S.A. setting the tune and stepping up its own military preparations in various parts of the world."

Does Ustinov believe, for instance -- as he asserts and Brown flatlyy denies -- that Brown supports NATO's achievement of "nucear superiority" over the Warsaw Pact? It may seem odd or phony to us that anyone should feel threatened by American actions that most of us see as reactive, lagging and unprovocative. But let us grant that Moscow's historical inferiority complex and fear of foreigners die hard, and that perceptions (ours as well as theirs) play tricks on truth.

Something else glints from Ustinov's statement. I don't mean just threat but alarm. I sense the forming of a question: has the Kremlin blown it? Has the Soviet Union, by its 15-year arms buildup, gone too far? Has it pushed the United States into the kind of foot-to-the-floor response that will nullify Soviet strategic gains, kick off a real arms race and end for 20 years the detente on which so many Soviet domestic hopes hang?

An experienced Politburo member, Ustinov knows that the gains sought by the Soviet Union's vast military investments could be washed out if the United States were to summon up a big new defense burst. It is precisely to preempt such burst that the Kremlin has talked up arms control.Yet even this administration, pushed by Congress, is drafting high-powered military plans all the same.

Ustinov knows some other things, too, better than we do: that the Soviet Union is surrounded by enemies and unreliable allies; that the Soviet civilian economy is stretched tight and structured for inefficiency; that the coming Kremlin succession will aggravate infighting over the budget; that Moscow will soon be buying oil in the world market; that a declining birth rate is pinching manpower; that discrimination against Jews is choking a major source of scientific talent, and so on.

In these circumstances, is it really to Moscow's advantage to take such a laughably lopside approach to the litmus issue of European nuclear weapons? does it not make sense to check signals across the board?

I am not predicting that the Kremlin has seen the light. It is at least possible, however, that the Soviet Minister of defense understands that a substantial a nd, to Moscow, disturbing U.S. response may be setting in. To that extent, the prospects for negotiation may be looking up.

At the Vienna summit, when Brown gave him a Polaroid camera "for verification by national technical means," Ustinov gave Brown as stuffed bear, the 1980 Olympics symbol, explaining that the Russian bear "is threatening only in evil times -- in general he is good and peace-loving." But of course that begs the question Ustinov appears to be pondering now: what kind of times are these?