IN the coming weeks, chemical weapons experts from the United States and Soviet Union will sit down in a historic meeting in New York. On their agenda: the exchange of detailed information about each other's poison gas stocks. This summit of specialists was agreed on by Secretary of State James Baker III and Soviet Foreign Minister Eduard Shevardnadze at their Jackson Hole, Wyo., talks. It represents a tentative step toward eventual reduction or elimination of superpower chemical bombs, rockets, and shells.
The US and the USSR have traded proposals for just such a bilateral cut in recent weeks. But both sides' offers are conditioned on moves by the other, and progress on mutual chemical weapons cuts doesn't look imminent.
Still, ``there's a lot of movement right now on chemical weapons,'' insists a US official, both between the superpowers and in Geneva, where the US and 39 other nations continue to struggle over a treaty that would flatly ban chemical weapons from Earth.
The New York meeting is being hailed by the US and the USSR as unprecedented, although the superpowers have shared chemical arms information before. An exact date for the meeting has not been set, according to administration officials.
It was set up by a memorandum of understanding signed in Wyoming which called for detailed data exchange and a series of visits by experts to chemical weapons plants in both countries next summer.
A second section of the memorandum calls for exchange of even more detailed information and short-notice, surprise inspections of chemical-weapons installations. But in an indication of how complex this area of arms control is, these further measures would not be taken until just before a Geneva treaty scrapping all poison-gas weapons is signed by the nations of the world.
President Bush, following on the heels of the Jackson Hole talks, offered in his UN speech to eliminate 80 percent of the US chemical weapons stockpile if the Soviet Union would do the same. He was trying to leverage a reduction he'll have to make anyway: Congress has agreed to allow production of new binary chemical weapons only if the Defense Department destroys 90 percent of its old poison stocks by 1994.
Foreign Minister Shevardnadze countered with an offer simply to scrap all superpower chemical arsenals - if the US stops its binary production. The Soviet Union says it has already stopped making chemical weaponry.
Both offers received lots of news play, as they were made in the glare of the UN forum. But since then not much has happened. The US has not formally replied to the Soviet counteroffer, according to a State Department official. The subject might come up in the New York meeting. It could also come up in Geneva in December. Multilateral meetings on the worldwide poison-weapons ban will resume then, and the US and the Soviet Union often huddle together over various chemical-related subjects on the edge of these talks.
Even if agreement were reached tomorrow, destruction of stocks would not. New US chemical demilitarization plants will not go on line until 1991 at the earliest, and the Soviets say they are in a similar situation.
Bush's UN offer was also aimed partly at the many other countries that will gather in Geneva. It was meant to help prod them along toward a sweeping chemical ban. Unfortunately for the president's purpose, revelations of another administration policy may have the opposite effect. Quietly, the US has decided that it should reserve the right to keep building modern binary weapons even after a multination chemical ban has been signed, say administration officials.
THE theory is that the US should maintain an adequate arsenal of new binary chemical weapons for deterrence purposes during the interim period between treaty signing and worldwide destruction of final stocks. Whatever the theory, third-world nations are not likely to buy it, claim US critics of administration policy. The draft text of the multilateral pact has long contained a provision saying that all countries would agree to stop production lines the day all sign on the dotted line.
``This is a treaty stopper,'' says Elisa Harris, a chemical-weapons expert at the Brookings Institution.
Bush officials may have pushed this decision because they feel a treaty may be only a few years off and US binary chemical production has fallen behind schedule. Currently, only one of three planned binary weapons, a 155mm shell, is in production. Problems with getting the right parts mean that the Army will not use up the money it allocated for 1989 155mm chemical shell manufacture until next summer, according to an Army spokesman.
Until a multination chemical-weapons treaty is fully implemented - and all countries capable of making such weapons are party to it - the US will retain 2 percent of its current chemical-weapons stocks, administration officials say.
``We won't go to zero until all chemical-weapons states go to zero,'' said Ron Lehman, director of the Arms Control and Disarmament Agency, in a meeting with reporters last week.
Meanwhile, Congress is trying its own approach. Both the Senate and House are working on legislation that would levy economic sanctions against any nation that employed chemical weapons.