As Americans whose collective experience includes service as secretary of defense and arms control negotiator, we take strong exception to The Post's editorial "The Missile Vote" (March 1).

After listing some of the numerous -- and we find compelling -- reasons why the MX missile should not be approved, the editorial then discards logic and says: "But the real world is a different place." We disagree. The real world -- the important one -- is that of military necessity and practicality, and on these counts The Post itself has judged the MX to be deficient. The MX will be a highly capable weapon in a fixed location of high potential vulnerability. It will be a first-strike weapon; it will surely be seen as that. And it will be a weapon that could provoke a nuclear war, not deter one. We do not see how these attributes can possibly enhance America's security.

We also do not see how questionable and -- in our judgment -- ephemeral negotiating considerations override these basic flaws. The editorial states, in essence, that we must have the MX because the Soviets have heavy missiles. This argument means that we must mirror-image our forces with those of the Soviets -- despite the fact that the United States has other, important strategic-force advantages, such as balance and greater overall invulnerability -- as well as superior bomber and submarine capabilities. This argument would also dictate that the United States have 200 Army divisions, a massive civil defense program and an extensive, expensive conventional continental air defense -- capabilities The Post has not chosen to advocate because, quite correctly, when choices about forces and weapons are being made, America does not need them for the job it has to do. Similarly, we were struck by the stark contrast, just 24 hours later, when the editorial page -- rightly and convincingly -- rejected U.S. acquisition of new chemical weapons for negotiating purposes or because the Soviets have them. Indeed, The Post's choice of words, with MX in substitution, would be the best rebuttal we could possibly write.

We also reject the proposition that the MX will serve as a useful bargaining chip. History has shown the difficulties of using deployed weapons as bargaining chips, since these weapons simply become another "essential" weapon with their own powerful momentum and supporters. They also trigger new Soviet programs. One need only cite the examples of MIRVs and the cruise missile -- weapons whose initial American gain is being duplicated by the Soviets at no small cost to our own security. The one bargaining chip example, so often cited in its defense, is, quite simply, factually incorrect. The Soviets agreed to negotiate on anti- ballistic missiles in 1968; the U.S. Safeguard ABM program was approved in 1969 -- not the reverse timing of which we are so often told.

Our experience has taught us that the practical value of bargaining chips lies in our ability to threaten their development and deployment. Once deployed, the chip is a weapon nearly impossible to halt.

Therefore, the "real world" of the MX missile, if approved, will be a weapon with tens of billions spent, with strong entrenched constituencies pressing for its continuation, if not expansion, and a bargaining chip that will have lost its ability to bargain because the Soviets will see it approved, they will know the economics and the politics, and they will develop their own similar program -- as they are already doing -- not meekly back down as wishful thinking would have us believe.

This leads to our final point on bargaining chips. We note that the editorial had to go back as far as July 1983 to find a presidential declaration that the MX will, in fact, be negotiable. We would draw the attention of all of The Post's readers to the fact that the most senior administration officials, including the president, have repeatedly stated that the MX is not negotiable, and that just two weeks ago the president's press spokesman refused to deny this. The editorial calls for a "freshening" of the president's 1983 statements. We believe that these statements of nonnegotiability more accurately reflect the eventual fate of the MX, and if that is the case, today's "chip" will be no bargain for the future of our nation. We urge Congress instead to pursue a different solution. If, in fact, the MX is to be regarded as a valuable bargaining chip, then it should be used seriously for bargaining purposes. Therefore, any congressional approval of funding for further MX deployments should be conditioned upon an undertaking by the administration to propose to the Soviets a ban on all new MIRVed ICBMS. The MX, under these conditions, would continue only if this proposal is rejected by the Soviets. Such a proposal, we believe, would be taken seriously by the Soviets. If successfully negotiated, it would serve our interests as well, stopping the deployment of new Soviet missiles. The MX would become, for once, a bargainimg chip that worked.