INDIA'S EXPLOSION of a "peaceful nuclear device" in 1974 shocked the founding members of the nuclear club into recognizing that the policies they had adopted to prevent the spread of nuclear weapons were not working. For the first time, they say the intimate connection that exists between some of the materials and technologies needed to run a commercial nuclear power system and those necessary to make a bomb. India had diverted a research reactor supplied by Canada and material known as heavy waste exported by the United States, both intended for peaceful purposes, to make its bomb. Accordingly, the nuclear nations joined in efforts to place more controls over nuclear exports, especially those connected to weapons technology.

These efforts were the silver lining of the Indian mushroom cloud, but in one sense they came too late. The message had already gotten across that exploding a nuclear weapon, far from inflicting political costs, had in India's case, actually enhanced its prestige. The United States, for one, never protested the misues of its heavy water, at the time or later. Correcting that mistake -- and trying to ensure that any other nation contemplating a nuclear explosion understood in advance that the political costs would be heavy -- has been the underlying purpose of all that has been done in the name of non-proliferation since.

But recent events in South Asia threaten to unravel a good deal of what has been accomplished in nonproliferation in the past few years. Pakistan, India's longtime adversary, is building a clandestine plant, the purpose of which is almost certainly to make the highly enriched uranium necessary for atomic weapons. All diplomatic efforts to alter Pakistan's course have so far failed. Across the border, equally determined negotiations to convice India to accept international safeguards on all its peaceful nuclear facilities have also broken down. An export license for nuclear fuel for India is pending before the Nuclear Regulartory Commission, and, under the law, it should not be approved unless there is reason to believe that the safeguards negotiations will succeed.

Especially in light of recent upheavals in Iran and Afghanistan, there are compelling reasons for the United States to preserve functional, if not warm, relations with both India and Pakistan. But it is increasingly doubtful whether Washington has the leverage to induce either of them to change its nuclear course. The United States may therefore have nothing left to do but to ensure that whatever neculear developments it cannot control in South Asia do minimal damage to its other non-proliferation objectives.

At the least, this means that further neclear shipments for India not be approved without a specific quid pro quo, and that a maximum effort be made to agree in advance with our European allies on the steps that would be taken if Pakistan were to test a nuclear weapon. To be taken by surprise once is human, twice is unforgivable.