Shooting down the ABM Treaty

The President's March 23 speech holding out the prospect of space-based ballistic missile defense systems also raised the possibility of future violations of the 1972 ABM Treaty with the Russians. But a truck may have been already driven through the back door of the agreement. Both the United States and the Soviet Union are building weapons - based on current technology - designed to shoot down aircraft or shorter-range missiles which, when improved in power alone, may be capable of intercepting SLBMs (submarine-launched ballistic missiles) as well as land-based intermediate-range and intercontinental ballistic missiles.

This raises serious questions about circumvention (or violations) under the Anti-Ballistic Missile Treaty of 1972: (1) Article III and the 1974 protocol permit only one fixed site ABM deployment on the national territory of each country; (2) Article VI prohibits the upgrading of surface-to-air missiles (SAMs) in that each party may not give missiles, launchers, or radars - other than ABM systems - capabilities to counter strategic ballistic missiles or their warheads in flight trajectory; and may not test them in an ABM mode; (3) Article VIII binds the US and the USSR not to transfer to other countries, and not to deploy outside their national territory, ABM systems or their components; (4) Article V prohibits the development, testing, or deployment of ABM systems which are sea-based, air-based, space-based, or mobile land-based.

The US plans to deploy in Europe in 1984 the Patriot surface-to-air missile (SAM), with deployment also intended in the US. In his annual posture statement for FY 1984, the secretary of defense described the weapon as the army's ''all-altitude air defense missile system.'' It has a multifunction, phased-array radar, and is designed to conduct multiple simultaneous engagements against high-performance aircraft. (It replaces Nike Hercules.) The launcher of the missile has four tubes. It is supposed to be the most effective American weapon against all air-breathing targets.

The Patriot is to be tested not just against aircraft, but also against ballistic missiles at White Sands - specifically, US intermediate-range Pershing IIs. But it will be described as having an ATM (anti-tactical missile) capability.

The Soviet Union has a new surface-to-air missile, the SA-10, which can engage multiple aircraft and possibly cruise missiles at any altitude - according to ''Soviet Military Power'' recently published by the Pentagon. Development of a mobile SA-10 is under way. The Soviets are also developing a new SAM, the SA-12, which has been tested against ballistic missiles. They claim it is only designed to counter ''tactical'' missiles.

In 1972, when transmitting the ABM Treaty to President Nixon, Secretary of State Rogers stated that each party had agreed not to provide non-ABM missiles, launchers, and radars with the capability to counter ''strategic'' ballistic missiles or their elements in flight trajectory. Yet, both of the above weapons, the US Patriot and the Soviet SA-12, may have the capability to intercept SLBMs and land-based intercon-tinental ballistic missiles (ICBMs). Or the PATRIOT could be used to counter SS-20s; and the SA-12 to shoot down Pershing IIs. Would this not make them ''strategic'' ABM systems?

If the US claims the Patriot is for European defense purposes (based in West Germany), it would run up against the ABM Treaty's prohibition on deploying outside the national territory the weapon limited by the treaty. Would the US tolerate the Soviets moving their new SA-12 system to East Germany, or Cuba - after they had tested it against ballistic missiles? Or countenance extensive deployment around the USSR?

Again, the ABM Treaty allows each country only one ABM site; the Soviets chose Moscow and the Americans selected an ICBM field in North Dakota. But, surely, a European-based ABM system which can shoot down, say, Soviet SLBMs fired from the Baltic or American SLBMs assigned to NATO, is a system that could be used against ''strategic'' ballistic missiles. The same can be said of ASBMs (air-to-surface ballistic missiles) which are also counted in the SALT II agreement. Further, the ranges of SLBMs and ASBMs can be shorter than Pershing or SS-20 intermediate-range missiles. For all practical purposes, ''anti-tactical'' missiles are strategic ABMs.

While we are all star-struck by the President's vision of ballistic missile defenses in space, we had best keep one eye on the qual-itative arms race down on earth. We must not permit the ABM Treaty - perhaps the most tightly drawn strategic arms control accord - to be whittled away. The President's speech rent the political fabric under the treaty, holding out the threat of a breakout in the future. But current weapon developments can gut the central provisions of a bargain that came close to being a real freeze on the arms race in strategic defensive weapons.

Let the administration prove that it is serious about maintaining the ABM Treaty of 1972, signed for ''unlimited duration,'' by trying to resolve these issues with the Russians in Geneva - now.