Without benefit of public discussion, the United States is on the verge of breaking a 10-year moratorium on the production of chemical weapons. The particular weapons involved -- a new type known as "binary" -- would make the actual use of chemical weapons more likely than before.

Binary chemical warheads consist of two canisters containing substances that individually are safe. When the shell is fired or the bomb dropped, a barrier between the two compartments ruptures. The two substances mix during flight, forming a new lethal chemical. Binaries therefore remove most of the disadvantages of chemical weapons to the user: they are much easier and safer to manufacture, store, handle, transport and eventually dispose of than ordinary chemical warheads.

The Army has been trying for years to begin building a binary production plant. But repeated budget requests were defeated by lopsided margins in Congress. As a further precaution, in 1975 Congress went so far to prohibit the future use of funds for production of lethal binary weapons unless the president first had explicitly certified that this was essential to the national security.

This year, without debate, the House has passed an appropriations bill containing funds to start building the production plant. The Armed Services Committee merely noted that "insofar as the committee is concerned," the 1975 prohibition "does not apply to the development of a production facility." Although the Senate has not yet acted on its military bills, informal polls of the likely conferees suggest that the senators will probably support the House position. If they do, production of chemical weapons could be resumed without a single legislator's having had to cast a recorded vote.

Congress is sliding casually toward a very important decision. It owes its constituents a great deal more before taking such an action. The arguments for and against taking this step need to be made -- out loud and in public.