THE national debate over the Strategic Defense Initiative (SDI) has been gaining momentum since President Reagan's 1983 ``star wars'' speech. Now it seems to be entering a new, more-intensive phase. Confusion in the administration as to the various meanings of the ABM Treaty has now raised fundamental questions among our NATO allies and within the Congress about the United States' commitment to international treaties. This has added to existing concern about the feasibility, survivability, and cost of President Reagan's vision for SDI. This is so because the SDI is an outgrowth of the antiballistic missile systems covered by the ABM Treaty, namely systems that can destroy incoming warheads.
On Oct. 6, national-security adviser Robert McFarlane dropped a bombshell when he asserted that the US was not legally bound by the ABM Treaty from developing the new, exotic ABM weapons envisaged in the SDI program. The zigzagging that followed now seems to have resolved into a curious, and as far as I know, unique position. The administration has told Congress and our allies that a new interpretation of the 13-year-old treaty shows that a ``broad'' interpretation is justified, which would allow the te sting and development of ABM systems based on lasers and particle beams. The administration, however, says that while it could legally go beyond basic research, it will not. That could change, it is implied, after the Geneva summit, or after the 1986 elections, or after the first SDI weapon is ready for tests.
State Department legal adviser Abraham Sofaer conceded to Congress that he could not name another instance where the official US interpretation of an international treaty and the US policy with regard to that treaty were at variance. Beyond the immediate arms control implications, the allies are understandably worried that if the United States can reinterpret this treaty, it could do the same with other international agreements, including whatever may come from Geneva.
While there may be some legalistic arguments about what exactly the ABM treaty says, the more basic question is: Why is the administration raising this issue now? Why should we question one of the few working arms control treaties weeks before President Reagan's first meeting with the Soviet leader? Would it not be better to suggest changes or clarifications at these talks?
At least one faction of the administration has little regard for arms control treaties and wants to base the future security of the country on space weapons. This view is receiving strong support from the defense industries. With the scent of a possible trillion-dollar program in the air, defense contractors are scrambling to get a piece of the action. Foreign support is being sought with the temptation of overseas contracts. Industry here and abroad knows that if the government pumps enough money fas t enough into this program, within a few years there will be a strong lobby which will make SDI hard to stop, even if it is not in the best national interest.
So even though the SDI is officially a research program, there seem to be many people who have already decided star wars can work. Congress has not; the scientific data are not yet that sanguine.
Many members of Congress are increasingly concerned about SDI. New studies, such as that recently done by the nonpartisan Office of Technology Assessment, seriously question the feasibility and advisability of the system. The OTA report concludes that the popularized notion of star wars as a ``shield'' that could render nuclear weapons ``impotent and obsolete'' is simply not possible. More likely, the SDI program could develop futuristic weapons for a new version of the ABM system proposed in the 1960 s -- a system that could protect our missiles against Soviet warheads.
But even this more-limited goal might not be worth the effort. The OTA and other analysts note that if both the US and the Soviet Union had ABM systems that worked, we might actually reduce our retaliatory capacity to respond to a Soviet first strike. Our defenses might protect most of our missiles over here, but they would be destroyed over there by Soviet defenses. The net result would be fewer US warheads striking their targets than if there were no defenses at all.
Moreover, if a space weapon can shoot down missiles, it can also shoot down other space weapons. Defense Secretary Caspar Weinberger contended in this newspaper recently that SDI is stabilizing and it ``could provide defensive security with resulting reduction in nuclear risk.'' The OTA report reached the opposite conclusion. It indicated that if both sides had space weapons, ``an extremely unstable situation would arise.'' Each side would have an incentive to ``use or lose'' its weapons.
There is also the question of money. The first seven years of SDI research are planned to cost $33 billion (fiscal years 1984-90). Full deployment of the system could cost $1 trillion. Where are we going to get these funds? Mr. Weinberger argues in the Monitor, ``Technologies developed through SDI research could be useful in European defense and have implications for conventional defenses . . . SDI capability against intermediate nuclear forces would enhance conventional deterrence by increasing surv ivability of NATO defenses in Europe.'' While some of this may be true, I am concerned, along with former Secretary of Defense James Schlesinger and the NATO commander, Gen. Bernard Rogers, that SDI directly competes for the resources needed for our conventional forces. Is the dream of an ABM system worth cutting our ability to meet the more likely threat of a conventional attack in Europe?
I am worried about possible violations by the Soviets of the ABM Treaty, such as their radar at Krasnoyarsk. But I am also worried about handing the Soviets a convenient loophole to deploy new ABM systems by our new ``reinterpretation'' of the treaty. Last month Weinberger sent all members of Congress a pamphlet on the Soviets' ABM program which warned of this threat. Now we seem to be giving them legal grounds to do so.
What happens now? Congress has trimmed the President's SDI budget this year, and future restrictions can be expected. There is broad support for a reasonable research program, and I agree with that. There is wariness over testing and deployment, and I agree with that as well. Budgetary and diplomatic considerations may weaken congressional support for SDI even as the administration and the defense industry try to build it.
President Reagan should use his present strong bargaining position to negotiate at Geneva a limit on the development of space weapons on both sides. In return he could get Soviet agreement for serious reductions in offensive nuclear forces. Mr. Gorbachev has indicated a willingness to do so, and Soviet concern over the administration's new interpretation of the ABM Treaty might encourage additional Soviet concessions.
If the present administration maneuvering is designed to gain negotiating leverage, it is brilliant. If it is the successful effort of a handful of officials to scuttle arms control talks in favor of SDI deployment, it is a tragedy not only for the United States, but for the world.
Charles E. Bennett (D) of Florida is a senior member of the House Armed Services Committee and a member of the Research and Development Subcommittee, which authorizes SDI funds.