This week the Senate will again confront the issue of whether to modernize America's inventory of chemical weapons. We want everyone to be clear as to what the issue is, as well as to what it is not.

First, the issue is not whether America should or should not have chemical weapons. We already have them, and so do the Soviets. And until a treaty can be negotiated for a complete and verifiable ban on all chemical weaponry (an initiative we strongly support), we believe that few Americans would favor a policy of unilateral disarmament in this area.

Second, the issue is not whether to develop a "new type" of chemical weapon or a more lethal one. At present our chemical deterrent is either stored in bulk or deployed in what are called "unitary" munitions: shells in which the chemicals are already mixed and, therefore, highly toxic. But bulk-stored chemicals cannot be delivered and thus obviously are not a credible deterrent. For their part, unitary shells are inherently dangerous, since any accidents or leakage from them could easily result in a major catastrophe, not only for the military personnel handling these weapons but for nearby communities and civilian populations as well.

Fortunately, another kind of chemical shell is available. In the "binary" shell, the toxic elements are kept separate until the projectile is actually fired. And because the chemicals are harmless until they are mixed, leakage or damage to the shells does not present a hazard. The issue that Congress will soon be deciding is whether to keep our chemical deterrent in the old and increasingly dangerous unitary canisters or whether to put it in the new and safer binary shells.

Another common misconception is that by moving to binary munitions, America would be increasing its stockpile of chemical weapons. In fact, just the opposite is true. Under the Senate Armed Services Committee proposal, for every binary weapon added to our inventory, the equivalent of four unitary weapons will be destroyed. In other words, not only would we have a safer deterrent, but we would also reduce the size of our chemical stockpile by 75 percent in the bargain.

In the past, some have argued that possessing chemical weapons provides no real deterrence. We believe that history indicates otherwise. Since World War I -- when the Allies produced and employed poison gas only after the Germans used it first and on a massive scale -- instances in which warring nations have each possessed chemical weapons (World War II, Korea, Vietnam) have resulted in neither side's using it. But in cases where only the Soviets or their allies have possessed chemical weapons (Afghanistan, Southeast Asia), there is strong evidence that they have indeed been used. If hostilities should ever break out in Europe, no one can say with certainty that the Soviets would use chemical weapons against the United States or its allies. But in our view, that gamble is simply not worth taking, especially since a quick escalation to nuclear weapons would likely result if we lost the bet.

A final argument often advanced against modernizing our chemical weapons is that doing so would seriously hinder our efforts to reach an agreement for their abolition. But this argument ignores the fact that the Soviets summarily dismissed the draft treaty the United States proposed at Geneva last year on this subject. It also ignores the fact that America's self-imposed, unilateral moratorium on chemical weapons production has now lasted for 16 years without any reciprocal action by the Soviet Union. And it ignores the historical truth that the Soviets negotiate seriously only when there is no advantage for them to do otherwise.

We are not suggesting that mrnizing our chemical weapons would be a "bargaining chip." But it might well be a bargaining catalyst -- and that alone would make the effort worthwhile.

We are keenly aware that the position we advocate entails a clear political risk for those who support it. But we also believe that our position is the right position from the standpoints of both safety and security.