INDIA'S NUCLEAR BOMB explosion of 1974 yielded two kinds of political fallout. It led countries that export nuclear materials and facilities for peaceful uses to seek new ways to prevent diversion to military uses. In that spirit the "suppliers" set up a kind of anti-proliferation cartel, and the United States passed its own control legislation, the Nuclear Nonproliferation Act, in 1977. At the same time, India's explosion kindled a desire to emulate its example in the Third World. In that spirit, Pakistan India's neighbour and rival, evidently determined to make its own atomic bomb.

The two developments collided publicly the other day. Under the 1977 act, the United States announced it was cutting off economic and military aid to Pakistan for that country's failure to put under international safeguards the uranium enrichment plant it has secretly been building; the plant could produce material for a bomb. American diplomats had tried to talk Pakistan out of its program. But the Pakistanis are frozen in distrust of India and, with their other difficulties, they evidently are not in a position to budge-least of all long as India maintained unchanged its status as a military-nuclear power. So as a matter of policy as well as law, the United States really had no choice except to act. Either this country is serious about non-proliferation, or it is not.

It is mystifying, nonetheless, that the cut should have been announced now. Pakistan is in convulsions over the execution of former president Bhutto: there could not be a moment when it is less likely to respond positively to pressure on the sensitive nuclear question. Did the State Department's left hand have any notion of what its right hand was doing?

Meanwhile, the Pakistanis note bitterly that aid has not been cut off to India. But the legislation mandating the cut was passed three years after India's blast. Anyway, India has its own dispute with Washington. The United States sends uranium to India under an agreement saying it must be fully safeguarded; otherwise, no more uranium. India, resisting full safeguards, says a fuel cutoff would abrogate its safeguards commitment. The two countries are bargaining intensely; the law sets a deadline of next March. The Pakistanis may find it harder and costlier than they imagine to build their own bomb, but India could surely reduce their incentive to proceed by coming to its own nuclear agreement with the United States. That is where statesmanship and true security lie.