ICBMs are, in this era, vulnerable to attack. As President Carter put it in his State of the Union Address in 1980:

"Without the SALT II limits, the Soviet Union could build so many warheads that any land-based system, fixed or mobile, could be jeopardized."

The significance of this vulnerability can be enormously exaggerated--as it was for years by MX proponents trying to get their missile approved. Or it can be played down--as MX proponents are trying to play it down now to get approval for deploying MX in the same "vulnerable" Minuteman silos. The window of vulnerability can be, and has become, a venetian blind.

Nevertheless, some vulnerability is there. And the obvious conclusion is to build fewer ICBMs, rather than more, and to shift reliance onto other arms of the deterrent. Moreover, for the ICBMs that are already built, one should attempt to secure some kind of arms control restraints to protect them. There is no lasting protection for ICBMs except through arms control.

A second obvious conclusion is that a competition in ICBMs plays into the Russians' hands. They are free from political and geographical restraints in such land deployment. Indeed, geography encourages them to emphasize land deployment, just as access to the oceans encourages us to rely more heavily on sea- based deterrents. Under these circumstances, it is a splendid example of hubris to see our strategists turning the question of land-based missile deployment into a question of national "will."

Under such conditions, we should make a serious effort now to control the ICBM race with arms control. We should, for example, seek to halt the new ICBMs permitted under SALT II until negotiations can define the context in which these ICBMs will be deployed. Both sides have proposed missile reductions; let them hold their new ICBMs in reserve while the negotiations proceed. And if at some point they are deemed to fail, then we should leave the land- based preponderance to the Russians--it only reflects a preponderance of vulnerability.

The Scowcroft Commission's approach is one that gives "modernization" clear precedence over either arms control or strategy itself. Desperate to win consensus, the report is willing to talk about arms control. But what it says is ill-defined and concerns the long-run future. Its single-warhead missile will itself cause arms control problems with its mobility. As Harold Brown admitted, it will also be "prohibitively" expensive in costs and land unless we "negotiate severe limits on the level of ICBM warheads." So why not negotiate now and save $25 billion or so on MX alone?

This MX decision is, in fact, a call to a land-based missile arms race. The commission says that it wants to deploy only 100 such missiles. But it says that if the Soviet Union engages in "major new deployments," and "refuses to engage in stabilizing arms control," we should "reconsider" this limitation. But the avowed purpose of the MX deployment is to encourage the Soviet Union to redeploy its ICBM force. Failure to deploy MX, the report says, would "undermine the incentives to the Soviets to change the nature of their own ICBM force." In short, we are using the counterforce capability of MX to force the Soviets to engage in new missile programs while simultaneously threatening them not to engage in ones we don't like. When would all this get straightened out? The commission wants an approach toward arms control in the "period" between 1987 and the early 1990s. This is too far off and too ill-defined to be taken seriously.

The last refuge of a poor decision is, invariably, a call for unity. Like lawyers unable to argue either the facts or the law, the strategic establishment has called for "national consensus" on the last and silliest of all the proposed deployments. Just as, during the Vietnam War, an entire American generation learned to question authority, so also will this MX consensus discredit an entire establishment of strategic analysts.

When an approach is bankrupt, the committees of clerks manning the executive branch are always the last to know. History shows that only the public, through the legislature, can put the coup de gr.ace to really major examples of executive branch mismanagement.

But I feel confident that, somewhere between the dying of MX and its death, Congress will recognize the obvious merits of arms control now. As with the ABM, only overwhelming opposition, and the imminent demise of a weapons system, can focus the mind of an administration and force it to negotiate.

Accordingly, in answer to the editorial challenge of The Post, I would argue that there is something "real and here and now the critics will accept" and that is negotiations now. Negotiate seriously over new ICBMs on both sides of all kinds or lose the MX without getting anything for it and, probably, in due course, lose the follow-on missile too.

The writer is director of the Federation of American Scientists.