You wouldn't know it from news reports, but most of the military plutonium stocks India dipped into for its recent nuclear tests came from a research project provided years ago by the United States and Canada. India had promised both countries it would not use this plutonium for bombs.

If Washington and Ottawa were now to keep India to its promise, and verify this, India would lose more than half the weapons-grade plutonium for its nuclear bombs and missiles. The United States and Canada should make this an essential condition for the lifting of economic sanctions.

The plutonium in question is the approximately 600 pounds -- enough for about 50 bombs -- produced in India's CIRUS research reactor since it began operating in 1960. This was an "Atoms for Peace" reactor built by Canada and made operable by an essential 21 tons of heavy water supplied by the United States. In return for this assistance, India promised both suppliers in writing that the reactor would be reserved for "peaceful purposes."

India used plutonium from this reactor for its 1974 nuclear explosion. When the facts emerged, Prime Minister Indira Gandhi insisted there had been no violation of the peaceful-use commitments because India had set off a "peaceful nuclear explosion." The Indian scientist then in charge, Raja Ramanna, now has admitted it was a bomb all along. And India now has declared itself a nuclear-weapons state on the basis of its current tests. With the decades-old "peaceful" pretense stripped away, the United States and Canada should make unambiguously clear that India may not use CIRUS plutonium for warheads or related research.

The fact that neither capital has uttered a peep about this matter is symptomatic of Western complicity in the South Asian nuclear crisis and of the present paralysis in dealing with it. There is also the matter of a 1963 agreement covering two U.S.-supplied nuclear power reactors at Tarapur and their fuel. The radioactive used fuel from these reactors is in storage and contains most of India's "reactor-grade" plutonium. India has said it will reprocess the used fuel to extract the plutonium for use as civilian power-reactor fuel. But reactor-grade plutonium also is explosive and, once separated, it could be used by India's scientists for rapid deployment in warheads. There is enough Tarapur plutonium for hundreds of them.

Under the 1963 agreement, India must get U.S. approval to reprocess. India disputes this and insists it is free to reprocess the used fuel at any time. The State Department, historically reluctant to tangle with India, rationalized Tarapur as an unnecessary irritant in U.S.-India relations and put this disagreement in the sleeping-dogs category.

In the history of U.S.-India nuclear relations, nothing stands out so much as India's constancy in pursuing nuclear bomb-making and America's nearsightedness about Indian intentions. India fought to weaken the charter of the new International Atomic Energy Agency in the 1950s. It was duplicitous in carrying out Atoms for Peace agreements in the 1960s. It undermined the Nuclear Non-Proliferation Treaty with its "peaceful" bomb of 1974.

Despite this history, each new generation of American policymakers thinks that by being a little more accommodating it will gain Indian restraint and acceptance of nuclear controls. The Indians (they are not alone in this) have for a long time played on that characteristically American self-deception that stems from a mix of idealism and commercial greed. It is not surprising that the Indians expect that game to continue.

The angry congressional reaction to discovering America's role in the 1974 test was the 1978 Nuclear Non-Proliferation Act. This barred nuclear reactor and fuel exports to countries such as India that refuse to accept full international inspections. But the State Department helped India get around the law by arranging for France and later China to continue the Tarapur fuel supply. Is it any wonder the Indians do not take us seriously?

Like India's 1974 test, the 1998 tests present a defining event in U.S. nonproliferation policy. We have failed to react sharply enough to head off Pakistani tests. But we still can be taken seriously in this region and by other aspiring nuclear states such as Iran. At a minimum we should insist that Indian plutonium covered by "peaceful purposes" agreements be unavailable for warheads, and that Tarapur fuel is not reprocessed to extract plutonium. This is by no means the whole answer, but there is no point in trying to "engage" India in new nuclear limitations if we do not enforce existing agreements. Victor Gilinsky is an energy consultant and Paul Leventhal is president of the Nuclear Control Institute. At the time of India's 1974 test they were, respectively, a member of the Nuclear Regulatory Commission and of the U.S. Senate staff.