The one-two punch in your Dec. 17 issue -- an editorial and an op-ed piece -- didn't lay a glove on the case for a comprehensive nuclear-test ban.

You challenged a test ban's relationship to the goal of nonproliferation. But the words of the Non-Proliferation Treaty of 1968 make the connection clear. To induce the rest of the world to join the treaty, those nations with nuclear weapons not only promised good-faith efforts toward disarmament but also reaffirmed their 1963 pledge in the Limited Test Ban Treaty "to seek to achieve the discontinuance of all test explosions of nuclear weapons for all time." Contrary to your writers' assertions, we should apologize for our failure to live up to our commitments, and we can expect those working to build their own bombs to find comfort in our behavior.

Keeping our word would cost us nothing in the safety and efficiency of our "nuclear umbrella." The United States now conducts only a few tests for safety and reliability. As a forthcoming report by Princeton scientist Frank von Hippel and others asserts, these could be rapidly completed or avoided by testing only non-nuclear components. By your talk of efficiency, I assume that you do not urge more kills per kiloton but refer to greater accuracy. But that is a function of delivery systems, not the warheads themselves.

As for the "nuclear umbrella," these weapons serve no military purpose other than to deter use by others. We can ensure such deterrence without testing new weapons and with only a fraction of our present nuclear forces. Further testing of nuclear weapons provides no support for our foreign policy, in the Gulf or elsewhere. Mushroom clouds make lousy umbrellas. -- Paul C. Warnke The writer was the chief U.S. arms negotiator under the Carter administration.