Soviet leaders have railed at the unfairness of the US START proposal that would reduce their ICBM (intercontinental ballistic missile) force, their strongest strategic arm, by more than one half. We need not worry much about the Soviet complaint - Moscow can be expected to complain whether justified or not - but we must be concerned about the damage the US proposal could do to America's own security.
Various commentators have already pointed out that the Reagan ''deep reductions'' in warheads and ballistic missiles could still leave each remaining US ICBM facing as many Soviet warheads as it does now - or more - and thus frustrate the main objective of the Reagan arms control plan: to reduce US ICBM vulnerability.
But this result will be prevented, administration officials contend, by a novel basing scheme for the new US MX ICBM that will render it invulnerable. Yet all the schemes which have been examined thus far have now been thrown out the window except one - called ''closely spaced basing'' (CSB) or ''dense pack.'' This scheme has so many technological fishhooks in it, however, implementation could amount to no more than a costly gamble.
The real problem is that the MX ICBM with its 10 warheads and devastating accuracy does not harmonize with the administration's arms control plans.
Any proposal of the US for an equal number of ICBM warheads on each side will increase the vulnerability of its own ICBMs as long as they have multiple warheads. Simple ratios between warheads and missiles compel it. The answer is to scrap multiple warheads; that is, terminate MX and either stick with the current Minuteman ICBM or go for a new ICBM with only one or a couple of warheads. A new ICBM could be much smaller and lighter, and that would make it more economical and easier to provide defensible basing.
An even more serious problem with the MX and the programmed Trident 2 submarine-launched ballistic missile in the Reagan arms control blueprint is that their accuracy poses a severe threat to the survivability of Soviet ICBMs. Why should we care? Because in strategic interfaces an unstable condition on one side can translate into a danger for the other side.
It would be costly indeed for the USSR to convert its ICBMs to less vulnerable basing. Economically, according to Reagan officials, the USSR is already in deep trouble. Moscow could seek a way out by converting to a ''launch-on-warning'' strategy, an alternative dangerously liable to misreadings and hoaxes, and therefore accidental war. The US could be unintentionally cinderized in a finale to its own arms control proposals.
Another unreality in the US START position is the assumption in the numbers proposed by the US that all Soviet warheads are targeted on the US or NATO - in other words, that Moscow has no other enemies. The Soviet Union has another feared adversary on its eastern flank - China - which now might have 150-200 missiles of varying ranges plus some aircraft that can inflict nuclear destruction on Soviet population centers and military installations. Ten to 15 percent of Soviet ICBMs, plus an undetermined number of Backfire bombers the US would classify as strategic, could be reserved to target this foe of the Soviets.
The Soviet Union will undoubtedly insist that its concern for the China security factor be incorporated in the final agreement before it will sign.
Both Britain and France, allies of the US under the North Atlantic Treaty, have nuclear forces that could inflict severe destruction on the Soviet Union. Great Britain's flag flies over four missile-launching submarines with 64 Polaris missiles aboard and a total of 192 nuclear warheads. Britain has plans to replace these in the future by highly accurate Trident 2 missiles when they become available from the US. Augmenting these forces are more than 50 Vulcan bombers which can deliver 150 nuclear bombs on Soviet territory.
France has even more formidable nuclear delivery capabilities. Five submarines carry 80 missiles, one large warhead each, plus 33 Mirage bombers and 18 land-based ballistic missiles all of which can hit Soviet targets. These impressive British and French nuclear arms are pledged under Article 5 of the North Atlantic Treaty to act in concert with the US because of an ''armed attack against one or more of them in Europe or North America shall be considered an attack against them all.'' The US argument that it cannot speak for its own allies because they are independent governments will not hold up. Before the final word of an arms control treaty is written their contribution to Western allied nuclear forces must be recognized.
Another gap in the US proposals now being discussed at Geneva is their failures to deal clearly with strategic bombers and the air-launched cruise missiles which they will carry.
President Reagan has vaguely said that they will be considered at some point. Unofficial reports say that the US, which is far ahead of the Soviet Union in these weapons both in numbers of deliverable warheads and technology, contemplates a proposal to have equal numbers of aircraft on both sides and to defer limitations on cruise missiles. Bombers and cruise missiles constitute an awesome arm of the US strategic ''triad'' and cannot be vaguely brushed aside at the negotiating table. Until the Reagan administration speaks forthrightly about how it thinks such weapons can be substantially controlled and reduced it cannot realistically expect to reach an agreement.