`Thresholds' the key to reducing strategic arms

The new buzzword is ``thresholds,'' as in ``thresholds list.'' At this point few understand the issue. But it is the linchpin for any reductions in the most threatening nuclear weapons, the strategic monsters.

The technology and some of the concepts are complicated. The ABCs of it look like this:

What are ``thresholds?''

The Soviets have proposed that the two superpowers define permissible test magnitudes for the coming decade for the various 21st-century technologies needed for ``star wars.'' Anything below a certain brightness of laser or aperture of mirror, they say, could be freely tested on earth or in space. Any tests above these negotiated ``thresholds,'' however, could be conducted only on earth.

What does that have to do with agreeing on the 50 percent cuts in strategic offensive arsenals that President Reagan and Soviet leader Mikhail Gorbachev are aiming for as a top priority?

The Soviets say that they dare not implement deep cuts in offensive weapons unless they are sure that strategic defense (otherwise known as an anti-ballistic missile or ABM system, the Strategic Defense Initiative, SDI, and star wars) will remain limited. Threshold constraints on SDI are the necessary precondition for deep cuts in offensive weapons, they maintain.

Cutting Soviet offensive arsenals when the United States is building a defense would increase instability in a crisis, the Soviets argue, and could be suicidal. If the US goes ahead and deploys strategic defense, the Soviet countermeasure will thus be to increase, and certainly not to decrease, offensive warheads. (The US says it would respond the same way if the Soviet Union deployed strategic defense.)

Therefore, Mr. Gorbachev is signaling Mr. Reagan that either we limit both strategic offense and defense and cooperate in destroying some 10,000 nuclear warheads between us, or we don't limit either defense or offense - and race each other to build another 20,000 warheads in the 1990s.

So that's why the 1972 ABM Treaty prohibited testing or deployment of ABM systems or components in space?

Yes. The intent was to prevent so much development of defensive systems or components that one side could ``break out'' of the treaty with a sudden deployment that would give it decisive military superiority over the other and thereby destabilize the nuclear balance.

But at the same time the treaty allowed enough research and development to be a hedge against breakout by either adversary by letting each side learn enough about new technologies to design countermeasures. But the treaty failed to specify just what constraints would make this distinction in the case of lasers, particle beams, or other ``exotic'' technologies that were only dimly perceived 15 years ago. This gap is what a thresholds list would seek to fill.

But would setting test thresholds kill Mr. Reagan's SDI program?

The most ardent fans of SDI say it would. The most ardent fans of arms control say it would not - and so do pragmatists who stand in the middle and support SDI research and the ABM Treaty.

The clearest example, according to one US official familiar with the Soviet list, is the Soviets' proposed ``restriction'' of kinetic kill experiments in space to velocities of 5 miles per second, achievable from satellites in low-earth orbits. With one satellite traveling 5 miles per second in one direction, and another traveling 5 miles per second in the opposite direction, and with further modification possible by changing the orbital plane, tests could be determined for any impact speed up to 13 miles per second - a velocity much greater than is needed for any SDI experiments planned over the next decade.

Moreover, Soviet negotiators have said this specification would in effect confer Soviet legitimation on such American SDI testing in space.

Will Reagan play the thresholds game?

Nobody knows. So far he hasn't. But so far he hasn't had the offer of 50 percent cuts in warheads dangled before him as concretely as the Soviets are doing now. What Washington pragmatists hope is that in this area Reagan might emulate his turnaround on higher taxes following the stock market crash, and after a year of adamantly vetoing thresholds, finally yield gracefully and change his position. Last month he hedged, for the first time, when asked about the issue by reporters. The pragmatists read this as a sign that he may finally be letting his moderate advisers pose the question in terms of its merits rather than just letting hard-line advisers pose it in the crude terms of killing or saving SDI.

If Reagan does decides to play, how fast could a US position on thresholds be cobbled together?

Within a few weeks. The Pentagon already has set criteria proving its planned SDI program remains within the ABM Treaty bounds. (The State Department has already worked out some threshold concepts of its own.) The opening US position would therefore be very easy to write, simply by using existing standards. Formulating the fallback position would be trickier.

Is there precedent for negotiating this kind of understanding under the ABM Treaty?

Yes. The Soviet-American Standing Consultative Commission (SCC) has modified or clarified ambiguous points in arms control treaties several times. To keep the ABM Treaty up to date with the latest technology - assuming both sides wish to do so - the SCC would probably have to start a rolling process under which new test thresholds for various technologies were negotiated every few years.

Then what would be the role of Senate approval?

The Senate would have to ratify the political decision to start this process, probably by ratifying the first agreed list of thresholds. But once consensus was achieved on the concept (as it presumably would be if Reagan agreed to it), then future modifications of lists could be entrusted by and large to the SCC.

Why are the Soviets so intent on striking a deal with this president?

They figure that - just as it took a conservative opponent of China, President Nixon, to recognize China - so it will take a conservative opponent of arms control to carry out arms control politically in the US.

But isn't it too late for a lame-duck president?

Granted, this is a high-risk gamble. If the 1980 campaign is any precedent, there is very little time left in the administration before the politicking of the presidential election runs amok with arms control.

On the other hand, in a period when Reagan especially needs a success, following the Iran-contra hearings and the stock-market crash, the pragmatists are arguing that he has victory within his grasp in arms control.

Moreover, by now the SDI program is far enough along for America's original euphoric expectations to have been scaled down to the point of suggesting the virtues of compromise to many scientists familiar with the difficulties. Yet it's also far enough along for the Soviets not to be as panicky about it as they originally were - and therefore to be more relaxed about the kind of restrictions they demand. This is evident in the concessions Moscow has made in recent months in dropping its insistence on a veto on SDI deployment following a ``thresholds'' regime of 10 years, and in making a thresholds offer of their own that is within reasonable negotiating range.

Is it star wars that brought the Soviets to these concessions?

Star wars and the accession to power of that innovative leader Mikhail Gorbachev. America's SDI powerfully focused Soviet minds and made them articulate their own interest in stability and in force structures that would avoid any temptation to go for a preemptive first strike in a crisis.