WITH President Clinton's decision in July to extend the current US halt on nuclear testing, prospects for a permanent, global ban on nuclear testing look more promising today than they have for more than a decade. Three other nuclear powers, France, Britain, and Russia, also have declared a temporary moratorium on tests. Washington has begun consultations with these nations and with the fifth declared nuclear-weapon state, China, on starting five-way talks for a comprehensive test-ban treaty (CTBT).
Despite the end of the cold war, a number of United States nuclear "hawks" still object to a test ban. They see it as a senseless restraint on US prerogatives that ultimately will damage American security and fail to contribute to nonproliferation. In fact, a CTBT will significantly enhance US security and that of our friends around the world. It is important, however, for both sides of this debate to recognize that the terms of that debate have changed.
For many years, advocates argued that a CTBT would reduce the threat of a catastrophic superpower nuclear exchange by making it much more difficult to deploy new, more destabilizing arms.
Today, however, the collapse of the Soviet Union has largely ended the superpower nuclear rivalry and, with it, the threat of global nuclear war. The security benefits for the US and the larger international community from this fundamental change vastly overshadow any added reduction in the likelihood of superpower nuclear war that a test ban may bring.
Indeed, when he extended the US testing moratorium in July, Mr. Clinton emphasized the halt's potential contribution to slowing the global spread of nuclear weapons. Here, the potential security benefits for the US and its friends are likely to be very substantial.
First, although a comprehensive test ban may begin with the five declared nuclear powers, it is generally assumed that the treaty also will be adopted by a substantial number of nonnuclear states. This will give the treaty considerable weight as an international norm.
Today, the three undeclared nuclear powers, India, Israel, and Pakistan, each could deploy nuclear weapons quickly in wartime. Yet they are not conducting tests for fear of international criticism. Among this group, only India is known to have conducted a nuclear test, one in May 1974.
A CTBT would greatly reinforce existing pressures on these countries to refrain from testing, even if they did not join the treaty. In fact, however, both India and Pakistan have declared in the past that they would join a test-ban treaty. Israel, too, might take this step.
As a result, a CTBT would slow development of next-generation weapons. India, Israel, and Pakistan rely on atomic weapons of the types used on Hiroshima and Nagasaki. None has yet developed far more destructive thermonuclear ("hydrogen") weapons, which would require full-scale tests. Moreover, while Israel apparently possesses atomic warheads for its missiles, India and Pakistan have not yet developed them. Progress toward this goal could be retarded, perhaps considerably, if full-scale nuclear tests wer e precluded.
Second, a CTBT could constrain states like North Korea, Iran, Iraq, and Libya that aspire to nuclear weapons. Some CTBT opponents argue that, like Israel and Pakistan, these states would not need to conduct tests to develop rudimentary atomic arsenals. A treaty, they reason, would do little to keep them from crossing the nuclear-weapon threshold.
Most experts agree that testing probably would not be essential. But it must be remembered that Israel developed its capability in conjunction with France; many believe that it received data from one or more French tests. Pakistan is thought to have received a previously tested design from China. Whether other states that lacked such help would have confidence in their nuclear weapons without a test is uncertain. India, which did not receive such aid, apparently considered a test necessary. Sweden was pl anning a test before abandoning its nuclear-weapons program in the 1960s. South Africa, however, which has just dismantled its small nuclear deterrent, had confidence in its nuclear arms without a full-scale detonation.
Even assuming additional states could cross the threshold without test detonations, if they were parties to a global test-ban treaty they too would be prevented from graduating to hydrogen bombs, and possibly to nuclear-tipped missiles.
Third, a CTBT as an international norm or as binding in particular cases, would have an impact on "inheritor" states, such as Ukraine, which split away from the former Soviet Union and is contemplating whether to take control of the nuclear arms remaining on their territory.
In most instances, the inheriting country could acquire only a fraction of the nuclear arsenal, infrastructure, and expertise of its parent. If a CTBT prevented the state from testing, it would have to recognize that inherited weapons would soon deteriorate and become unreliable.
Yet the country that the inheritor would usually be most interested in deterring - its former parent - would possess a far larger, more diverse nuclear arsenal, as well as decades of nuclear-weapons-manufacturing and testing experience. The parent, too, would be constrained by the test ban; but its history as a nuclear power would give it much greater confidence in the reliability of its nuclear arms over time.
This ought to make the potential inheritor realize that the costs of seizing nuclear assets on its territory would far outweigh the all-too-transitory benefits.
Finally, and perhaps most important, progress toward a CTBT may be the key to a substantial extension of the Nuclear Non-Proliferation Treaty (NPT), a matter that must be decided in 1995.
The treaty is the centerpiece of global efforts to halt the spread of nuclear arms. By requiring comprehensive nuclear inspections, it places significant constraints on the nuclear aspirations of states like Iran, Iraq, Libya, and North Korea.
The nonnuclear-weapon members of the treaty have long demanded that the nuclear members - especially the US and Russia - ban nuclear tests to demonstrate that they are living up to the NPT's mandate that they negotiate in good faith toward ending the nuclear arms race.
As a practical matter, the START I and II treaties will be much more valuable as steps toward nuclear disarmament than a CTBT. Over the years, however, the test ban has acquired such political symbolism that progress toward a ban has become a virtual precondition for a substantial extension of the nonproliferation pact.
Moreover, doubt exists whether the US-Russian START I and START II treaties will take effect, since they require cooperation of Ukraine, which has become increasingly balky. Accordingly, the CTBT could well be the lynch pin for retaining the nonproliferation pact in the decades ahead.
Conservatives are correct when they assert that a CTBT has costs. US advocates of further testing argue that tests are needed to improve the safety and ensure the reliability of US nuclear arms. In effect, these advocates argue that testing helps maintain the credibility of the US nuclear deterrent, on which NATO, Japan, South Korea, and other US friends rely. The point is valid. But as Clinton determined in July, the nonproliferation benefits of a testing halt considerably outweigh the possible benefits
to the US of further detonations.
If the value of a CTBT is determined by its impact on US security, then its benefits in slowing advances by de facto nuclear powers, retarding the emergence of new nuclear countries, discouraging inheritor states from taking control of nuclear assets on their soil, and solidifying support for a substantial extension of the Non-Proliferation Treaty make it a clear winner.