"It kind of amuses me," President Reagan told a Newsweek interviewer, "that everybody is so sure I must have heard about ['Star Wars'] -- that I never thought of it myself. The truth is I did."

Well, I believe it. That is, I believe it is quite in keeping with the Reagan presidential style that he did not know government (and private) scientists had been hard at work researching anti-missile defenses well before he came into office -- and that the Soviets had begun even earlier looking into lasers and particle beams and other high-tech devices for destroying incoming nuclear missiles or warheads. Pride of authorship, then, helps explain the depth of the president's personal involvement.

And that, combined with the irrepressibility that is part of Ronald Reagan's charm, helpsexplain how a futuristic research program in its infancy has been transformed with one stroke into a heaven-sent propaganda opportunity for the Soviets -- and a needless, added complication to arms control negotiations that are already forbiddingly complex.

Publicly, administration officials play down the potential for trouble. Even the Soviets privately conceded to American officials that there is no way to verify a ban on research. Nor can the Soviets deny at the negotiating table that they are doing the same thing themselves. The Europeans, playing it cool, have dutifully supported a research program while muffling (for the time being) their deep concerns about the long-term strategic implications for their own security.

But privately, top officials agree that by the manner that Reagan chose to share his distant dream he released a genie that cannot now be rebottled -- a collection of uncertainties and anxieties on the one hand, and expectatons on the other, that could profoundly affect the course of the Geneva talks. To see why requires a second look at what Reagan said in his now-famous address to the nation from the Oval Office on March 23, 1983.

At first glance, you have to wonder why there was so much fuss. The section on "Defensive Systems" was tacked on as a tranquilizer for public support of a "major effort" to "restore our military strength." Only at the very end did Reagan get around to raising the vision of a world without nuclear weapons. For the most part, he was careful to talk only about strategic ballistic missiles -- not all nuclear weapons.

He said it would be a "formidable technical task," that it might not be done before the end of the century and that along the way the United States would retain the "nuclear deterrent and . . . a solid capability for flexible response." He reassured America's allies that the United States would remain in a position to honor its commitments to use this country's strategic offensive nuclear power "to deter attacks against them." We would continue to try to negotiate nuclear arms reductions.

Had he stopped right about there, it's entirely possible most people would have taken it as a titillating glimpse of something that might happen in the 21st century. But then came the high drama. First there was a "call upon the scientific community who gave us nuclear weapons . . . to give us the means of rendering these nuclear weapons impotent and obsolete."

Second came the hard news: "Tonight . . . I am directing a comprehensive and intensive effort to define a long-term research-and-development program to begin to achieve our ultimate goal of eliminating the threat posed by strategic nuclear missiles." And then the closing crescendo: "My fellow Americans, tonight we are launching an effort which holds the promise of changing the course of human history."

By the time the inevitable background briefers were through explaining the high technology of lasers and particle beams and all the rest, the nickname -- Star Wars -- had been indelibly stamped on a project that the administration would like to have us think of as "Star Peace." Instead it was officially named the Strategic Defense Initiative, which only reinforced the sense of something new, immediate, mysterious -- and somehow threatening.

The Soviets reacted in record time: SDI would "open the floodgates to a runaway race of all types of strategic arms, both offensive and defensive" -- the same argument made by both American and European critics. Many Europeans are equally unsettled by the prospect that SDI might work. With both superpowers safe under nuclear defense "bubbles," the Europeans' deterrence against the Warsaw Pact would be dependent upon a conventional force level they can't afford. Even conventional war, they argue, would leave them devastated beyond anything they suffered in World War II.

It would be foolish, then, to count on the latest refinements of the original Reagan formulation to put the Star Wars genie back in the bottle. As a Soviet propaganda ploy, it remains available as evidence, however phony, that the United States, by seeming to be doing something out of the ordinary, is spoiling prospects for progress in the Geneva talks.