Almost three years ago, the president and Congress agreed on a solution to a problem that has vexed this country for more than a decade -- what to do about land-based missiles in an era of rapidly increasing missile accuracy.

The agreed solution was designed with a vitally important goal in mind: to increase the stability of the strategic balance and thus reduce the chances of nuclear war. The program to produce this result contained three elements: 1)deployment of 100 MX missiles in Minuteman silos; 2)deployment of a small, single-warhead missile now commonly known as Midgetman; and 3)an arms control agreement that, among other things, was based on counting not launchers, but warheads of roughly equivalent size. We strongly reiterate our support for all elements of this program.

Two elements of the program have not come to pass. An arms control agreement has not been achieved, although the administration did modify its negotiating approach. Congress has refused to deploy over half of the 100 MXs. It now appears that the future of the third and vitally important element -- Midgetman -- may be threatened by some, both within the administration and Congress.

The current assault on the Midgetman focuses on two elements -- its mobility and its cost. The administration has proposed a ban on all mobile missiles, ostensibly because of the difficulty of verification. Mobility does worsen the problems of verification.

However, the motivation for barring mobile missiles becomes more understandable if the true intent of the administration is to provide survivability by defending with SDI an ICBM force deployed in super-hard silos. But while super-hardening may be attractive if it proves to be cheap, in the race between accuracy and hardening, accuracy will almost certainly win eventually.

SDI is not the only alternative for defending ICBMs. Conventional terminal Ballistic Missile Defense (BMD) can make an important contribution to improving the survivability of land-based ICBMs, especially in shelter-based modes. But with either SDI or conventional BMD as part of our survivability program for ICBMs we would be facing many unstable and dangerous transition years before arriving at convincing stability.

In any event, we should welcome, not fear, a Soviet move away from the behemoth SS-18 in its fixed silos tow MX-size) and initially less-accurate mobile missiles. In a more stable, small, mobile ICBM environment, even the requirements for verification become somewhat less rigorous.

The other principal criticism of the Midgetman relates to its cost. It is in truth expensive -- but not more so than other ICBM systems for an equal number of surviving warheads, if one makes reasonable assumptions about Soviet-and U.S.-system performance. The objective of the Midgetman deployment, however, is not economy but survivability and stability.

Some advocates of scrapping the current Midgetman program propose as an alternative placing several warheads (MIRVs) on a considerably larger mobile missile. It has long been recognized that a silo-based missile carrying many warheads is destabilizing, because attack on one aim point can destroy many times the number of warheads used in the attack. However, when a missile is based deceptively or on mobile launchers, this dangerously destabilizing character of MIRVing is sharply attenuated. This is because the only present means of attack on such a deployment is to spread the attacking missiles evenly over the entire area in which the deployment occurs (barrage attack). Thus the only relevant number becomes the equivalent megatonnage of warheads in the deployment, not the number of warheads per missile.

While accepting the validity of this theoretical position, we believe there are two compelling counterarguments against a new three-warhead, 75,000-pound missile -- one political and one substantive.

To abandon the present Midgetman program and start all over to build political support for yet another in the painful series of "solutions" to the ICBM problem would, in our opinion, put the entire future of ICBMs in the gravest jeopardy. Such a high-risk course might be justified were the substantive aspects of the issue strongly oriented in that direction. But the net of the substantive arguments also indicates continuation of the current Midgetman program.

A new missile program could lead to a two- year delay in the date for initial deployment. The larger MIRVed missile is not significantly cheaper than the Midgetman, especially if it is compared to a conceivable two-warhead modification that could be developed if future circumstances dictate. But most important, the larger missile sacrifices flexibility.

We are in an era of dynamic technological change, which argues powerfully for maintaining a high degree of flexibility. To risk that flexibility by shifting to a much larger, less mobile, MIRVed missile in the name of economy appears to us truly to be false economy. Flexibility includes, at a minimum, ability to make use of the road network as well as air transportability to other regions of the country, e.g., to areas where forests and other features could lend cover, if it were needed in the future.

A minimal increase in design weight of the Midgetman (on the order of 7,000 pounds) could be accommodated without loss of essential mobility or flexibility. This would be a prudent move, enabling the incorporation of decoys or penetration aids if needed to cope with the possible deployment of Soviet ballistic missile defense. In our judgment, no other significant changes are needed in the program at this time.

The question of ICBM modernization has been on the nation's agenda for nearly 20 years. This suggests that there is no unique technical solution that can simultaneously satisfy the objectives of an adequate capability to ensure deterrence, low cost, and stability. In our view, the Midgetman system possesses the balance of capability, flexibility and broad political support that makes it the system of choice for the future.