A comprehensive test ban doesn't remove a single weapon.

Nuclear freeze advocates are trying to revive one of their pet policy proposals: a comprehensive nuclear test ban. {Paul Warnke, op-ed, Dec. 9}

The reason being given by those who wish to downgrade maintenance of the U.S. nuclear stockpile is twofold. One part is "the disappearance of any real Soviet threat." The other is the argument that the ban would be a useful arms control measure "to discourage nuclear proliferation." Neither of these reasons is legitimate.

Let's take the nuclear proliferation argument first. The Nuclear Nonproliferation Treaty obligates its parties, among them the United States and the Soviet Union, to pursue good-faith efforts toward disarmament. Some people have erroneously equated this treaty obligation with a requirement for a comprehensive test ban. No matter that there have been real accomplishments in the field of disarmament -- the intermediate-range missile treaty, the accord on conventional force in Europe, the U.S.-Soviet chemical weapons agreement, the soon-to-be-completed START agreement -- these people contend that unless the United States undertakes a comprehensive test ban, the nonproliferation treaty will be at risk.

This fall there was, to be sure, an attempt to hold that treaty hostage to a comprehensive test ban. The incident occurred at the review conference on the nonproliferation treaty in Geneva. There, by virtue of the requirement for consensus, Mexican ambassador Miguel Marin-Bosch successfully blocked a final document (a report ordinarily issued at the end of a treaty review), arguing that no consensus could be reached unless the United States bowed to pressure for a comprehensive test ban. Marin-Bosch was isolated at the conference and failed to muster support for his efforts, but he has vowed to continue his campaign at the next nonproliferation treaty review in 1995. That is the year that parties to the treaty will decide for how long it is to be extended. The Mexican ambassador's threat is that unless the United States takes action on such a ban, the treaty will be made to suffer.

Obviously a comprehensive test ban is very important to Marin-Bosch, who describes it as a means of limiting the technological prowess of the United States. But is it really important to other states that are parties to the nonproliferation treaty? Marin-Bosch's isolation at the treaty review session is one measure that it is not. There are others. Take, for example, my experiences with foreign representatives on the subject.

Throughout 1989, I was the U.S. official responsible for preparations for the 1990 nonproliferation treaty review conference. I talked extensively with representatives of signatory governments about what they viewed as the most important agenda items for the then-upcoming conference. The bottom line was that a comprehensive test ban (CTB, as it is often referred to) did not make the list of priorities; in fact, it was scarcely mentioned unless I brought it up.

Instead, countries were worried about issues that directly affect their national security. Arab states want Israel in the nonproliferation treaty; African nations want South Africa in; East Asian countries want North Korea to comply with the treaty's requirements. As one leading diplomat from a nation very active in the treaty said to me, "Look, a CTB is not really important to my country because it does nothing to diminish the nuclear threat we face. It isn't even real arms control. It is mostly a stick with which opponents beat the U.S. government."

The official had an interesting point: a CTB does not constitute arms control. It does not get rid of a single weapon. Nor does it diminish the threats that make the weapons necessary. Instead, a comprehensive test ban would actually generate doubts about whetherthe U.S. nuclear arsenal is safe, reliable and effective. Thus it would be highly destabilizing. (Incidentally, even Soviet technical experts recognize the need for nuclear testing to ensure reliability. The U.S.S.R. announced that its Oct. 24 nuclear test was to "confirm the reliability and increase the safety of nuclear weapons.")

Let's turn to the other reason offered to rationalize a cessation of testing: the Soviet Union supposedly is no longer a real threat. Under the Strategic Arms Reduction Treaty, the United States and the U.S.S.R. will have the same ceilings on numbers of warheads and delivery systems at lower levels. This is worthy of note, but we cannot forget that, with the exception of its Bear G bombers, all Soviet strategic systems will be modernized. Making these forces even more threatening is the fact that many of the systems will be mobile and hard to verify or find in the event of hostilities.

By contrast, U.S. systems will be mostly old. And the United States will probably not have mobiles. Thus the perception of threat has diminished primarily because of Soviet economic problems, good will and the image of a single man -- Mikhail Gorbachev. The actual strategic capability of the U.S.S.R. has not lessened. The nuclear threat to the United States today is greater and more capable than ever.

If a comprehensive test ban is not a good idea, what should be the next steps on nuclear testing limitations? The prerequisite should be that any additional steps build on what has already been done.

On Sept. 25 the U.S. Senate ratified two treaties with the Soviet Union that limit the power of underground nuclear explosions to 150 kilotons (the Threshold Test Ban Treaty and Peaceful Nuclear Explosions Treaty). The ratification followed lengthy, difficult negotiations to craft verification measures. The two-page text of the Threshold Test Ban Treaty is followed by a 107-page verification protocol. There is now a need to absorb the lessons of practical application of these verification measures and to obtain broader adherence to these already achieved limitations.

This means that the rest of the world, including the other nuclear weapons states, should catch up with the United States and the U.S.S.R. For example, neither France nor China is a member of the Limited Test Ban Treaty, which limits nuclear tests to those conducted underground. All nations should express support for this treaty by signing it.

Second, now that the Threshold Test Ban and Peaceful Nuclear Explosives Treaties have been ratified by the United States and the U.S.S.R., there should be an effort to extend the same 150-kiloton testing limit to other existing and potential nuclear weapons states. France and the United Kingdom already appear to comply with the 150-kiloton yield restriction. It should not be a giant step for these two, China and the non-nuclear-weapons states to become party to these treaties.

To some, gaining additional adherents to existing treaties may not seem like a top priority. But they should remember the lessons of the Intermediate Nuclear Forces Treaty. In that case, the Unites States and the Soviet Union banned intermediate-range ballistic missiles. Now that those weapons are gone from U.S. and Soviet arsenals, missiles of that range are being acquired by countries worldwide. The United States must make sure that controls and limitations it accepts itself are shared by the world and not shouldered by the United States and the U.S.S.R. alone.

The writer is a former assistant director of the Arms Control and Disarmament Agency. She is now with the National Institute for Public Policy.