The time to negotiate is now

Diplomacy and force, as Henry Kissinger has pointed out, have been incorrectly regarded as distinct and successive phases of policy. The watchword of United States officials in the early cold war period was ''negotiate from strength'': First, concentrate on building up a strong defensive position against the Soviet Union, thereby physically containing it; then, and only then, engage in serious diplomatic exchanges with it.

The strategy of the US government for dealing with the Soviet Union at the present time, it would appear, is similar. The Reagan administration's attitude has been well characterized as ''spend first, talk later.'' On this theory, a sound as well as satisfactory diplomatic relationship with Moscow must follow major progress toward completion of a long-term rearmament program, including construction of a 600-ship Navy, the B-1 and Stealth bombers, a land-based MX missile battery, and a futuristic ''star wars'' system for the interception and destruction of weapons in outer space. All the Russians ''understand,'' it is said, is force. Words are superficial.

The pitfalls of a strategy of force-before-diplomacy, in both the logical and the chronological senses, are several. One is that the priority given to the military buildup, and the official concentration on it, tend to delay the formation of realistic, specific, concrete negotiating plans. The authority of the would-be negotiators - in the State Department or Arms Control and Disarmament Agency - can itself be undercut during such an interim. What diplomacy there is in a military buildup phase is often largely reactive. It is a response to domestic demands for a peace expression or a counterploy to some Soviet diplomatic initiative, which, because the American side is not ready to negotiate, must be dismissed as a ''peace offensive.'' The result: a devaluation of diplomacy.

A second danger arising from the negotiation-from-strength doctrine is, ironically, that the ''strength'' acquired will be of the wrong kind. That is, the military programs may not serve the real purpose of military defense. Preparedness involves much more than the exploitation of new technologies. It involves the actual capacity of men to fight, and to remain in the field - that is, personnel and logistics. These relatively invisible components of military strength may have more weight in the scales of international diplomacy than do such ''counters'' as warheads and launchers, although they are not conventionally so assessed in comparisons at the negotiating table. Because they are directly related to defense, rather than ''deterrence,'' they are less likely to be accumulated simply in order to be negotiated away. They are in that sense more ''serious.'' To an adversary, they are also more credible, without being provocative.

This brings me to a third risk in the relentless pursuit of demonstrable military superiority for the purpose of converting it, later, into diplomatic success. It may be premised on a profound misreading of the Soviet character, and it may therefore produce just the opposite reaction from the one intended. There seems little doubt that the current American military buildup has impressed the Soviet leadership. Foreign Minister Andrei Gromyko's recent protestations at the UN, objecting to ''the militarization of outer space,'' are evidence of this. The fact that he also called upon President Reagan at the White House, thereby assisting in his reelection bid, further indicates anxiety. These gestures do not, however, warrant the conclusion that the Soviet leadership will succumb to pressure. Rather, it may concentrate on redressing the balance it has struggled to achieve.

A glimpse of the Soviet psychology may be gained from a recent statement reportedly made by a Soviet official in Moscow. ''Of course Reagan's program is not war,'' he admitted. But then he added, his voice suddenly rising in emotion: ''He is trying to tell us that the Soviet Union cannot be a superpower. He is trying to beat us down, to damage us politically and economically, after we have worked so hard to establish equality. We can't let him get away with that, and we won't.''

Thus the conspicuous accumulation of US ''strength'' may have the effort of challenging the Soviet Union to even greater military exertions, not cowing it into diplomatic submission. The time when the US can ''negotiate from strength'' will thus be postponed, raising the question of whether the very idea isn't an illusion.

Why is it important for the US to negotiate arms control agreements? At one time, when the negotiation-from-strength idea was first conceived, it was possible for the US and its Western European allies to achieve security by their own efforts, by relying upon exclusive possession of the A-bomb and the defensive wall of NATO. Diplomatic agreement with the Soviet Union was not in fact really needed.

Today, as a result of the overlapping of US and Soviet spheres of interest and the vulnerability of both countries to intercontinental missile attack, their security situations are interdependent. ''The problem,'' said a Soviet official, ''involves the size of the planet. It is too small. You Americans think you can be secure at our expense. That is impossible. We both can only be secure when we both feel secure.''

Moreover, the rapidly advancing technology of armaments, particularly the introduction by the Soviet Union as well as the US of cruise missiles (hard to verify) and also the exploration by both sides of space-oriented missile defense strategies (hard to rely upon), threatens the whole framework of the existing Soviet-US arms-control regime, including the bedrock 1972 antiballistic-missile (ABM) treaty. The issues in future arms control negotiations, if delayed further while dubious and probably unusable ''strength'' is built up, may be so complex as to be incapable of resolution.

The time, therefore, to negotiate a comprehensive agreement with the Russians is now, on the basis of such considerable force as we and they already have. A serious diplomatic initiative is required, involving the whole Western Alliance. Winston Churchill's advice in a speech of Oct. 9, 1948, is perhaps more pertinent today: ''No one in his senses can believe that we have a limitless period of time before us. We ought to bring matters to a head and make a final settlement, we ought not to go jogging along, improvident, incompetent, waiting for something to turn up.''

We want to hear, did we miss an angle we should have covered? Should we come back to this topic? Or just give us a rating for this story. We want to hear from you.