In moving toward a major breakthrough on strategic arms reductions, let us not forget the need for some modest but important steps in the interim. In this, consideration should be given to the ratification of two negotiated and signed accords limiting nuclear weapons tests, the Threshold Test Ban (TTB) and the Peaceful Nuclear Explosion (PNE) treaties.

The TTB and the PNE were negotiated and signed between 1974 and 1976 by the Nixon and Ford administrations. The TTB prohibits all weapons tests with yields greater than 150 kilotons. The PNE accord places the same constraints on so- called peaceful nuclear explosions. The Soviets have looked favorably toward PNEs and the United States has not. The United States has concluded that in most instances chemical explosives are sufficient for civil projects, and they avoid the radioactivity problems associated with PNEs. For this reason, the PNE treaty will have a greater impact on Moscow.

Some quarters in the bureaucracy advocate that we not ratify the TTB and PNE so that we can retain the option of testing high-yield weapons. But as Gen. David Jones, chairman of the Joint Chiefs of Staff, has indicated, there are no plans for such tests; nor is there any real need to conduct them. Assuring reliability of our current stockpile of weapons can be achieved under the 150-kiloton level. Moreover, the Soviets are in a better position to profit from a move toward high-yield testing than is the United States. Moscow has ready-made facilities for such tests; we would have to start from scratch. There are few guarantees that Congress would fund such a program if we rather than the Soviets initiated testing above the threshold.

More important still is the likely impact of the 150-kiloton level upon the Soviet arsenal. The Soviets have long held a preference for multi-megaton weapons. These agreements would, therefore, be far more restrictive on them. If doubts on weapons reliability arose, this would first occur in Moscow. In the long term, moreover, the agreements might add to strategic stability. As new weapons came on line, their warheads would have to be tested to assure reliability. Likely Soviet doubts on the effectiveness of untested weapons might act as an incentive to move away from monster first-strike warheads.

Perhaps the most important provisions in these agreements deal with verification. The TTB provides for the exchange of geological and other test-related data required to assure compliance. The PNE's verification provisions are unprecedented. For the first time, the Soviets have agreed to on-site inspection.

The Reagan administration has made Soviet cooperation on the exchange of military data and on intrusive verification a litmus test of Soviet sincerity in arms restraint. The president's important strategic reductions initiative will depend on progress on these issues. The PNE and TTB offer Soviet concessions on both counts.

Support for ratification of these agreements has recently come from a broad spectrum of individuals, "hawks" as well as "doves." The group includes a stream of witnesses from the administration and the wider national security community who have testified before the Senate Foreign Relations Committee.

Since 1976 we and the Soviets have lived by these agreements--neither side has tested above the 150-kiloton level, and both have issued statements promising to adhere to the threshold as long as the other side does the same. But only ratification would bring the real benefits. Only then would the Soviets provide the data promised during negotiations and only then would they be bound to allow on-site inspection.