As American and Soviet officials resume negotiations in Geneva on reducing strategic arsenals, many experts feel that the nuclear superpowers need to be talking about a more fundamental issue.
It is fine to seek ways of reducing existing missile warheads and bombs, they say. But there needs to be a resumption of the stalled effort to limit nuclear weapons testing and thereby head off the newer generations of highly destabilizing weapons that threaten to undercut whatever deterrent balance exists today.
Tomorrow marks not only the return to Geneva of the United States delegation with some new faces and more ''flexible'' instructions from President Reagan. It is also the 20th anniversary of formal US ratification of the Limited Test Ban Treaty, in which the US, Britain, and the USSR agreed to end above-ground nuclear tests. Arms control advocates in Congress and elsewhere are using the anniversary as a rallying point to press for a Comprehensive Test Ban Treaty that would stop all new weapons testing.
''Developments in nuclear weapons technology since the signing of the Limited Test Ban Treaty have not enhanced deterrence but instead have contributed to the development of nuclear warfighting strategies,'' a group of former US arms control officials said Wednesday. ''A test ban now would help prevent development of the so-called third generation of nuclear weapons that may lead to a further erosion of the nuclear threshold and make nuclear war more likely.''
The Reagan administration, breaking the pattern of every administration since Dwight Eisenhower's, is not seeking such a treaty. There are at least four reasons for this: Mr. Reagan's commitment to modernize US strategic forces, which still requires much weapons testing; the doubts the White House has about being able to verify such a treaty; pressure from the President's political right to reveal alleged Soviet violations of existing treaties; and reluctance to weaken the US nuclear deterrent in the face of what are felt to be clear Soviet advantages in conventional forces.
This is a politically difficult position to defend in light of peace activities in Europe and the US, as well as attempts by Moscow to play up to these movements. At the United Nations this week, Soviet officials repeated their earlier calls for a ''freeze'' on the testing and deployment of nuclear weapons.
On the other hand, the history of attempts to limit weapons testing and control the deployment of strategic weapons has been checkered at best. There is growing evidence that the USSR in fact is stretching - if not crossing - the limits of existing treaties. All the more reason, test ban advocates say, to press for strict and verfiable limits on such tests.
There are growing efforts in the House of Representatives and in the Senate to revive the stalled US-Soviet-British talks on a comprehensive test ban, and new suggestions about how one of the stickiest issues - verification - could be resolved.
Former SALT II negotiator Ralph Earle II and Peter Staugaard of the Center for Foreign Policy Development at Brown University advocate a ''Quota With Advanced Notification Test Treaty.'' This would limit countries to just a few nuclear tests a year and require them to notify other signatories of test dates and locations. Verification would be by ''national technical means'' (satellites , third-country listening posts, and air samples) and tamper-proof seismic devices.
The Senate resolution calling on Mr. Reagan to resume test-ban negotiations has 37 sponsors, and House sponsorship of a companion measure now numbers 125. Proponents plan to lobby their colleagues on the issue over the Columbus Day congressional break next week in hopes of convincing House and Senate leaders to schedule hearings.
Proponents see this as a ''good middle ground'' between those wary of arms control and advocates of the more sweeping nuclear freeze measure. They also argue that a ban on further nuclear weapons testing would be advantageous to the US, which is ahead of the Soviet Union in such advanced technology aspects of weapons design as miniaturization. And they assert that superpower testing limits would help curb the spread of nuclear weapons to other countries.
''A total ban on testing would have a positive effect on nonproliferation efforts, one of the arms control goals emphasized by President Reagan in his recent UN speech,'' said a group of former officials now affiliated with the Arms Control Association. These include former Arms Control and Disarmament Agency directors Gerard Smith and William Foster.
But advocates also admit that the Comprehensive Test Ban issue appears stalled for the moment, secondary to debates over aid to El Salvador, US marines in Lebanon, and MX missile production.