Charles Krauthammer {op-ed, Oct. 6}, referring to a provision offered by Sens. Sam Nunn and Carl Levin, wrote, "To legislate the Soviet position of a delicate arms control issue {i.e., "a narrow interpretation of the ABM Treaty"}, in the midst of negotiations, is simply irresponsible." But the provision in question legislates no interpretation of the treaty. The administration has regularly stated that while it favors a broader interpretation, it will respect the traditional reading. The Senate provision upholds the president's two-year-old policy of observing the traditional interpretation and provides a procedure to expedite legislative consideration if he should propose to change it.

The Senate Armed Services Committee endorsed the Nunn-Levin language specifically "without prejudging the wisdom and desirability of undertaking testing, development and deployment of mobile/space-based ABMs using exotic technologies. . . ." It is strange to portray as confrontational the Senate's willingness to leave the issue for a later day, as the administration itself has proposed.

More important, in aligning the defense authorization with the administration's stated guidelines, the Senate effectively rejected the longstanding Soviet demand for a treatment of the Strategic Defense Initiative more restrictive than that provided under the traditional interpretation of the ABM Treaty.

It may be no coincidence that the Soviet stance on the ABM Treaty appears to have changed significantly during the Senate's consideration of the Nunn-Levin provision. In Washington, Soviet Foreign Minister Eduard Shevardnadze seemed to accept the treaty's original reading. If the Soviets now embrace the traditional interpretation, then the Senate's approval of Nunn-Levin may well have generated more movement than the administration achieved in years of Geneva talks.

Sen. Nunn, Mr. Krauthammer said, wants to give away what Ambassador Paul Nitze would negotiate in exchange for deep cuts in offensive forces. But numerous reports have indicated that, as Secretary of State George Shultz told a House committee, "we don't think any further negotiations are necessary." How could Senate action jeopardize negotiations that no one is conducting? Read fairly, what the Senate has done is to create a context that improves the likelihood such talks will finally begin. It has also provided substantial SDI funding -- more, in fact, than would be forthcoming without a frank understanding between the branches about the program's direction. ALTON FRYE Washington Director, Council on Foreign Relations Washington