INDIA'S NUCLEAR explosion in 1974 jolted the nuclear supplier nations into a more serious appraisal of the dangers posed to all of them by the spread of nuclear weapons. But after a relatively brief spasm of activity, the Western suppliers of knowledge, materials and nuclear technology -- and the Soviet Union -- fell back to casually ignoring what their exports were leading to. Iraq was and perhaps still is pursuing what one administration official has called a "Manhattan Project-type approach" to nuclear weapons. But Iraq is by no means alone. Israel's raid should reawaken concern for a number of similar situations developing elsewhere in countries where ostensibly "peaceful" nuclear research and energy projects are giving those host countries the wherewithal to produce nuclear weapons.

By far the most urgent concerns imminent nuclear tests in both India and Pakistan -- possibly, in India's case, within months. No one can look on the prospect of a nuclear-armed Asian subcontinent with any sense of security or, considering the region's intertwined ties to the United States, the Soviet Union and China, much hope for international stability. A second Indian test would certainly doom any further efforts to halt Pakistan's weapons program. A Pakistani test would spur on India's program and, as the first so-called "Islamic bomb," light a dangerous new spark in South Asia and the Middle East.

The Indians, having used American heavy water and training with a Canadian reactor in making their first explosion, are in a position to make a second from their own resources. The Pakistanis have received crucial training and plans in various European countries. They have been able to build their own small reprocessing plant from plans for the commercial-sized plant the French intended to sell but cancelled under earlier American pressure. They have secretly bought equipment all over the world. The source of the spent fuel from which they might reprocess plutonium is unclear.

Pakistan may also be the source of a Libyan bomb. As the principal supplier of funds for the Pakistani weapons program, Libya may well have negotiated for the right to one or more of whatever Pakistan is able to produce. Also, the Soviet Union is building a reactor in Libya similar to the one the French built in Iraq, the kind that runs on highly enriched weapons-grade uranium and converts that fuel to plutonium at a high rate. The status of this project is unclear to us. But even though the Soviet Union has a better record than the West in keeping tight control over nuclear weapons technology, the frightening posibility exists that circumstances will put a nuclear weapon in Libyan hands.

In South Africa, the situation is different. That nation, endowed with unlimited supplies of uranium, is thought to possess all the necessary know-how to make nuclear weapons, and it may have secretly tested one. But if ysouth Africa, like Israel, whose nuclear program is almost two decades old, is already a covert nuclear power, there is still much to be lost by its becoming a self-announced one. India, Pakistan, Libya and South Africa represent -- at least to public knowledge -- the principal current worries. There may be others, and more will surely arise unless the nuclear suppliers, acting in concert, develop new policies commensurate to the threat and, for once, persevere in them