A TIMELY move by Australia has breathed new life into negotiations on one of the most important arms-control treaties of the post-World War II era.
A model draft treaty submitted by the Australian government aims to circumvent hundreds of minor disagreements among the 38 nations meeting in Geneva to ban the testing of nuclear weapons. If the major differences that remain can be ironed out, a 50-year dream of statesmen and arms-control advocates could be realized by fall.
''The Australian draft has cleared away a lot of the underbrush and simplified the basic work that remains,'' says Jack Mendelsohn, deputy director of the private, Washington-based Arms Control Association (ACA).
Negotiators at the Conference on Disarmament are seeking to conclude a consensus draft by the end of June. If they succeed, it can be submitted to the United Nations General Assembly for endorsement in September. A formal signing ceremony would be held soon afterward.
Together with the indefinite extension of the 1968 Nuclear Non-Proliferation Treaty (NPT), which was approved by 178 nations last year, the Comprehensive Test Ban Treaty (CTBT) would be one of the major milestones in the effort to contain the global spread of nuclear weapons.
US and private arms-control experts say four hurdles have to be cleared before the treaty can go to the UN:
Scope of the treaty. The United States, Britain, and France want the treaty to mandate a total, or ''zero-yield'' test ban. China wants to leave the door open for ''peaceful nuclear explosions,'' which experts say would be indistinguishable from military-related explosions and which one senior American official compares to having ''a friendly punch in the nose.'' In the end, China is expected to concede the point. President Boris Yeltsin has said that Russia, the fifth declared nuclear power, also favors a total ban.
Entry into force. John Holum, director of the US Arms Control and Disarmament Agency, says support of the five declared nuclear nations - the so-called P-5 - is ''indispensable'' to the US. But differences remain over how many other countries should ratify the treaty and whether the list needs to include the three ''undeclared'' nuclear states - India, Pakistan, and Israel - and several ''threshold'' states, like Iran, which soon may have the ability to build a nuclear weapon.
Compliance. The main disagreement is over the precondition for conducting emergency ''on site'' inspections by the implementing organization created in the treaty to monitor compliance with the CTBT.
Several states, including China, India, Pakistan, and Iran, say the body should be allowed to conduct emergency inspections based only on information gleaned from its own monitoring system. The US, Britain, France, and Russia insist that more reliable and sophisticated ''national'' intelligence, such as information gathered by the CIA - be allowed.
The Australian draft splits the difference, allowing national intelligence if the commission approves.
Nuclear disarmament. India, which in 1954 became the first nation to call for a comprehensive test ban, insists on linking conclusion of the CTBT to complete nuclear disarmament. The idea is roundly rejected by the P-5 and has drawn almost no support from nonaligned states, which share India's goal but which do not want to sacrifice the test ban treaty to achieve it.
Under the rules of the disarmament conference, India could stand in the way of the consensus needed to send the treaty to the UN. Alternatively, India could refuse to sign the treaty, as it - and its archrival, Pakistan - have refused to sign the NPT.
The CTBT would be weakened if India, an influential ''undeclared'' nuclear state, refuses to support it. American officials partly attribute New Delhi's hard line to pre-election posturing. Parliamentary elections will be held in India by June.
Four of the five declared nuclear states have pledged to halt all nuclear testing through September. The fifth, China, has said it will continue testing but will stop when the treaty is approved.
The US has announced plans to proceed with a ''sub-critical'' experiment in June at the Nevada site where nuclear tests have been conducted since the 1950s. The planned experiment will not violate the zero-yield standard.
But ''holding tests at the Nevada site will send a wrong signal at a delicate stage in the negotiations,'' says Daryl Kimball, associate director for policy at Physicians for Social Responsibility, a Washington-based group that advocates nuclear disarmament.
Mr. Holum predicts the treaty will be ''all but completed'' by March 29, when the current session of the disarmament conference expires. After consultation with their governments, the delegates will reconvene May 13 and stay in session until the end of June.
''It's going to be a master stroke of diplomacy if all of the threads can be pulled together on this time scale,'' says ACA director Spurgeon Keeny.