PRESIDENT Clinton's decision to seek a comprehensive test-ban treaty brings within grasp a policy goal of nearly 40 years' standing. Since the administration of Dwight D. Eisenhower, the United States has recognized that prohibiting nuclear- weapons testing was critical to preventing the spread of those weapons.
But various concerns always got in the way - verification questions, assertions that test explosions were needed to prove the bombs would work, or cold-war incidents that soured the political climate. The latter ranged from the downing of a U2 spy plane in the 1950s to the 1979 Soviet invasion of Afghanistan.
The obstacles have largely disappeared in the 1990s. Some tough persuasion could lie ahead as the US tries to bring all members of the ''nuclear club'' aboard. France has already said it favors a comprehensive test ban (though, ironically, it wants to finish its highly controversial series of Pacific tests first), and Britain will follow the US lead. Russian and China can probably be convinced, despite the latter's ambiguous desire for ''peaceful'' testing.
Mr. Clinton took the most sensible route toward a test ban by opting for zero exceptions. Some in the Pentagon wanted a testing threshold of explosions equal to 500 tons of TNT, rather than a total ban. That was strongly opposed by many non-nuclear nations. Another option was a much lower limit, perhaps a few pounds of TNT. But such tiny blasts couldn't verify the readiness of large weapons, and they would have little research value. ''True zero'' made the most sense.
To reassure the Pentagon, Clinton has agreed to build a new installation where the reliability of the US nuclear arsenal can be assessed by means other than explosion. And he has promised to take seriously the ''supreme national interests'' waiver always included in such treaties. This would allow the US to resume testing should an extreme need arise in the future - an unlikely occurrence.
Nonexplosive methods of determining if weapons will work are well established and should put to rest the objections heard from a few members of Congress.
A comprehensive test ban treaty would be evidence that a new world order may yet be hammered together, piece by piece. Thanks to Clinton, the treaty negotiators in Geneva, whose work had slowed to a crawl, finally have something to run with.
Thanks to Clinton, the treaty negotiators finally have something to run with.