THE FACT that George Shultz and Andrei Gromyko have agreed to meet in Geneva in January to discuss arms control is going to cause a lot of excitement in Washington. We'll have optimistic backgrounders from the White House, hair-raising Evans and Novak columns predicting treacherous sellouts and lots of speculation about superpower rapprochement. And when all of this has passed, we will still have a difficult, dangerous Soviet-American relationship dominated by suspicion and distrust.

Think about it: Friday's newspapers carried banner headlines announcing -- as if it were big news -- that the American secretary of state and Soviet foreign minister will meet in Geneva to talk about arms control. Isn't this just what they're supposed to do on a regular basis? Well, it used to be. But now it is big news that they'll do it again, because both sides have so thoroughly botched up their relations in the last five years.

The meeting in Geneva on Jan. 6-7 may be a procedural breakthrough, but it foretells no substantive progress on the increasingly difficult problems of controlling nuclear arms. The shape of the table has been agreed to, but what is to transpire across the table? We shouldn't be surprised if nothing significant transpires for a long time.

The case for pessimism is strong, probably compelling. It is based on factors at work in Moscow and Washington that are obscured by the swirl of leaks and posturing public statements that dominate the flow of "news" on these subjects.

The most important of the factors influencing events in Washington is a dirty little secret shared by people all over town who work on and worry about the arms control problem. You can learn about it -- only in private, of course -- from former secretaries of state, secretaries of defense, national security advisers and others, Republicans and Democrats alike. You can even hear the secret whispered occasionally by veterans of this administration.

The secret is this: the Reagan administration does not have a national security policy. Doubters should refer to Nicholas Lemann's brilliant profile of Caspar Weinberger in the October Atlantic Monthly, a long article which demonstrates that the Reagan-Weinberger defense policy consists entirely of spending money on weapons.

Starting from a questionable perception that the Soviet Union had acquired military strength that put the United States at a distinct disadvantage, the administration set out to spend its way out of "inferiority." The result has been acquisition of the B-1 bomber, the MX missile, new carrier task forces for the Navy and an approach to arms control consisting, so far, entirely of efforts to placate European and American critics who sought to portray the administration as indifferent to real negotiations.

We're getting the new hardware, and we have dispelled any notion that the United States might be a patsy. But if you talk to Soviet officials, you learn that they believe Jimmy Carter succeeded in dispelling such notions during 1980, when he reacted angrily to the Soviet invasion of Afghanistan. Carter's MX, the Olympic boycott and the grain embargo made a strong impression in Moscow. Reagan could have achieved his goal of "standing tall" much more cheaply by capitalizing on those moves to demonstrate his strength and perseverence.

Instead he spent billions that have not made the United States significantly stronger. The Reagan MX program, now just 21 missiles to be placed in fixed missile silos theoretically vulnerable to Soviet attack, does not significantly change the strategic balance. (Carter's "racetrack" MX, abandoned by Reagan, was intended to hide the missile from Soviet attack, and would have given us a theoretically invulnerable land-based missile capability.) The B-1 bomber will last longer than B-52s now in service, but adds no signifcant new military capability. (The next generation of bombers -- called "Stealth" because their design will make them extremely difficult to locate on conventional radar screens -- will add a useful new capability, but by building B-1 first, the administration probably put off the day when Stealth will come into service.) The new 400-ship Navy would equip us nicely to refight World War II, but what is the chance that we will face that prospect?

The most bizarre aspect of today's situation is the fate of the notorious "window of vulnerability," a specter worthy of the little boy who cried wolf. This one was never easy to explain. It involved the fact that during the mid-1980s, the Soviet Union would have so many nuclear warheads atop super- accurate intercontinental missiles that it could contemplate launching a surprise attack against American intercontinental missiles, supposedly confident that they could wipe out all of ours using only a fraction of their own forces.

This "window" was an oft-used argument against the SALT II treaty signed by Carter in 1979. It became a campaign slogan for Ronald Reagan, who promised to close the window. Today it gapes as wide as any doomsayer ever predicted; this morning, the Soviets do enjoy a huge numerical advantage in warheads on land-based ballistic missiles, an advantage that has grown markedly during the Reagan presidency.

Happily, even the president and Weinberger have stopped worrying about it. The problem was never more than theoretical; to believe in it, one had to believe that some American president would absorb a huge nuclear attack and then decide not to retaliate with our many, still usable submarine-based missiles and bombers, out of fear that the Soviet second strike would be even more devastating than the first.

This was once explained to Sen. Paul Laxalt (R-Nev.), Reagan's close friend. After hearing that the danger of a "window of vulnerability" depended on the theory that an American president would absorb a nuclear attack and decide not to retaliate, Laxalt observed: "That's crazy."

Crazy it was, but that window of vulnerability was the moving force behind the Reagan administration's initial "strategic doctrine." Its burial ought to be followed by the articulation of a new doctrine, but it hasn't been.

Instead the president has gone off on an entirely new tangent, introducing the idea that we might build an invulnerable defense against missiles -- the "star wars" idea. This has the advantage of creating a whole new technological game on which to spend hundreds of billions more, but that's what Reagan always said was wrong with SALT-style agreements -- that they simply created excuses for redirecting the arms race, and failed to stop it.

Another aspect of the current situation in Washington is the absence of players in this administration who have a realistic set of goals for arms control talks, or know how to push an agreement through this city's many centers of power.

Judging by Strobe Talbott's "Deadly Gambits," an authoritative account of arms control politics in the first Reagan administration, there is only one senior official in the administration who combines the knowledge, vision and bureaucratic skills needed to advance a clear arms control position. He is Richard Perle, assistant secretary of defense for international security policy, and he opposes U.S. concessions that would induce the Soviets to make real deals.

Perle is a controversial figure, one widely distrusted and strongly disliked by proponents of traditional arms control, but he deserves full credit for intellectual consistency and political persistence. He knows what he doesn't want, and he knows how to block those who favor what he opposes. He apparently enjoys the full confidence of his boss, Weinberger, and he is ideally placed to derail any attempt by more moderate figures in the administration to move toward realistic negotiations. This, according to several of his friends , is one reason why Lawrence Eagleburger, the former deputy secretary of state, resigned this year. Eagleburger, it is said, concluded that those like himself who wanted to negotiate seriously with the Soviets could not overcome the obstacles thrown in their path by Perle and his allies.

Only an activist president or a resourceful bureaucratic infighter on the Henry Kissinger model can bring arms control negotiations to fruition, especially in a conservative administration heavily populated with people who don't trust the Soviets to keep any agreement and who fundamentally don't want one.

The Reagan administration has forced the Russians to eat a little humble pie by agreeing to the January meeting in Geneva (they previously said they would boycott negotiations until NATO withdrew its new medium-range missiles from Europe). But what comes next? If President Reagan has any clear idea about how to procede, he has yet to reveal it. Administration sources say there has been no fundamental reassessment of U.S. bargaining positions -- positions Alexander M. Haig described as non- negotiable in his recent memoirs.

Of course it was impossible to make any progress without getting the Soviet Union back to the table, so last week's announcement is a welcome first step. But it is many miles to the finish line, and for the United States, all the difficult steps remain in the future. A pessimist seems justified in wondering whether this cast of characters -- without a gifted conceptualizer in its ranks, led by a president with a tenuous grasp of strategic issues, with literally no experience at thrashing out a tough bargaining position that is bound to be controversial in Washington -- will be able to take those difficult steps in the coming months, even in the coming four years.

The real obstacles to new arms control agreements and more constructive Soviet-American relations are huge. Consider a brief listing:

How do we overcome our own past rhetoric? Are we now willing to accept big Soviet advantages in land-based missiles and "throw weight" (the weight of warheads and targeting devices their rockets can deliver) in return for our advantages in bombers, cruise missiles and submarine-launched missiles? Or do those imbalances still represent "fatal flaws" to the SALT II treaty and any successor agreement, as Reagan has argued in the past?

No matter how well the talks in Geneva go, the fundamental asymmetry between the superpowers will remain. Our forces are different; they have banked heavily on land-based, large missiles; we have invested in our "triad" of land- based and submarine-based missiles and bombers. We won't be able to keep all our advantages while depriving the Soviets of theirs. But this administration has given no hint that it is ready for tradeoffs that acknowledge Soviet concerns.

How do we overcome suspicions about Soviet cheating on past arms agreements? Having made so much of "verification" -- the ability to confirm that the Soviets are adhering to an agreement -- while raising serious questions about Soviet compliance with past agreements, have we forfeited any chance of comprehensive agreements in the future?

There are three alternatives on this issue. One is to go back to a more flexible definition of verification, accepting agreements that are difficult but not necessarily impossible to cheat on because the risks inherent in cheating far outweigh the potential benefits to be gained from deception. The second is to decide that because there will always be some chance that the Russians can cheat, we can sign no agreements. The third is to persuade the Russians to allow extensive on-site inspection to drastically minimize the chance of cheating. The third would be the best, but it is also the most improbable.

What sort of a better relationship do we want -- something like detente of the 1970s? Assuredly not -- it promised much too much, and delivered too little. But who has defined a good alternative that stands a chance of winning political acceptance in this country -- and particularly from Ronald Reagan's staunchest supporters on the far right? And what about the Russians? They are having serious troubles in Moscow; their leadership is uncertain, their economy is faltering, their diplomacy has been a miserable failure. Yet they have an overriding interest in proving -- to themselves, and to the rest of the world -- that Reagan's tough-guy approach to them doesn't work. They've made a procedural concession by agreeing to go to Geneva in January, but that should not be confused with substantive concessions that would reward Reagan for the hard line he has taken for four years. The Soviet side will be looking for American concessions in Geneva, while American negotiators will be waiting for the Russians to blink.

Of course both sides retain their freedom of action. The Reagan administration could change its stripes; the Kremlin could cry uncle. Flip-flops are possible, just not likely. In this round, the pessimists have been dealt most of the high cards.