Superpower arms accord: quite close?

The chief puzzle left after an astonishing summit is why Washington and Moscow are so dug in on ``star wars'' positions that are not very far apart. One of the more plausible answers is that President Reagan and Soviet leader Mikhail Gorbachev made such pell-mell progress on arms control in Iceland that both sides need a pause to sort out just where they are after several good nights of sleep.

This interpretation cannot be specifically confirmed in Washington. But on-the-record statements and background interviews with officials who participated in the summit tend to support it.

A review of current positions shows how close the two sides are to sweeping arms control agreement:

On the most acrimonious point, Mr. Reagan's Strategic Defense Initiative (SDI, or star wars) the issue, surprisingly, is not deployment. Moscow does not demand non-deployment at the end of the 10-year observance of the 1972 Anti-Ballistic Missile (ABM) Treaty that is now under discussion. It asks only that the two sides negotiate about SDI stationing at the end of the 10 years. In Reykjavik, Iceland, according to a senior official who was there, the Soviets focused on what happens during those initial 10 years virtually to the exclusion of what happens afterward.

The main differences that do persist on the ABM Treaty banning space-based strategic defense that do persist concern how long a non-withdrawal pledge would last and precisely what constraints on SDI testing would prevail during this period of ``non-abrogation.''

Going into Reykjavik, the United States was offering not to abrogate the ABM Treaty for a term of 7 years. As it currently stands, either side may abrogate with a six-month notification.

At Reykjavik, Mr. Gorbachev insisted on non-abrogation for 10 years and made this a condition for acceptance of the other framework agreements reached by the working group at the summit. The Americans, perplexed by his adamancy, did not say no. Instead, they countered by agreeing to 10 years only on the utopian condition that strategic nuclear ballistic missiles be reduced to zero during this period.

Differences over just what specific constraints would apply to SDI testing while the ABM Treaty remains in force are far more obscure. The US said it ``would strictly adhere'' to the ABM Treaty, Assistant Defense Secretary Richard Perle told a press conference. Another official who participated in the Iceland negotiations indicated that this meant strict adherence in terms of the old intra-administration controversy over strict or loose interpretation of the ABM Treaty.

The strict version (which the administration says governs its policy, though not its legal interpretation of the treaty) holds that Agreed Statement D on exotic new technologies would fall under Article V's prohibition on testing of ``ABM systems or components which are sea-based, air-based, space-based, or mobile land-based.'' The looser interpretation -- which the Defense Department champions -- holds that new technologies developed since 1972 are free of such restrictions.

Curiously, according to a senior official, the Soviets in Reykjavik were far less interested in discussing these interpretations (and how much they would limit SDI testing) than they were in discussing the generalities of Article I. Article I bans territorial missile defense of a country as a whole (as distinct from point defense of military or single-city targets).

Gorbachev did demand that SDI testing be confined to the laboratory. But it was not clear to US negotiators precisely what he meant by this. American negotiators understood it as a bid for even greater constraints on SDI testing than a strict interpretation of the ABM Treaty would require, but they did not know what concrete restrictions this might entail.

The Soviets, although they entered into more-complex discussions about SDI than ever before, seemed surprisingly unfamiliar with the specifics of the ABM Treaty interpretations. They did not raise the key questions of where the line is drawn between components (which under the treaty may not be tested) and subcomponents (which are not restricted). Nor did they spell out what their definition of ``lab'' testing would be.

Apart from SDI, the two sides made what both are calling historic progress on strategic offensive weapons and on Intermediate Nuclear Forces (INF or ``Euromissiles''); they also agreed on some modest final steps on nuclear test restraints.

On strategic offensive weapons, the Soviets basically accepted the US framework of 50 percent cuts down to equal numbers of 1,600 strategic nuclear delivery vehicles with 6,000 warheads. The numbers in subcategories remained to be worked out, but the Soviets have agreed to discuss subcategories, and also offered significant reductions in warheads on their 308 SS-18s -- a ``heavy missile'' that is a monopoly of the Soviet Union.

The Soviets say that long-range submarine-launched cruise missiles must be verifiably limited; the US says this is impossible. At Reykjavik the two sides committed themselves to achieving a mutually acceptable solution.

On strategic bombers, a sophisticated counting system was agreed on for the first time. At a strategic seminar this week, according to a listener present, chief working negotiator Paul Nitze described the counting system like this: Any strategic bomber without air-launched cruise missiles (ALCMs) would count as one warhead; any ALCM-loaded plane would count as the sum total of its ALCMs, plus one for the plane.

At Reykjavik, the US dropped its insistence on a ban on mobile missiles, a category in which the Soviets are beginning to take a hardware lead.

On Euromissiles, Gorbachev surprisingly accepted the longstanding US proposal of zero ``long-range'' INF (LRINF) in Europe, with a ceiling of 100 in Soviet Asia. In return, the US could keep 100 LRINF in the US.

Still to be determined are collateral restraints on short-range Euromissiles. The US has proposed a freeze on such missiles in ranges of the SS-23 and up, or about 500-1,000 kilometers. In essence Moscow accepts the idea of ``follow-on'' negotiations on this shorter range, but has not committed itself to negotiations on those of even shorter range, down to 150 kilometers.

Washington and Moscow differ on what a freeze on shorter-range missiles would mean. The Soviet Union says it should apply to present levels on both sides. The US says it must mean a global ceiling for both at the current Soviet level. This would permit the US to build up to the current Soviet level in Europe if it chooses.

The two sides also have different positions on the duration of a freeze; the US insists that a freeze must must last until some other agreement replaces it.

A broad understanding was reached on the concept of LRINF verification. A senior official cautioned against exaggerating what was achieved, but noted that there was general agreement on the principles of ``data exchange before, during, and after,'' on on-site inspection, and on dismantling or destruction of excess weapons.