Undeterred by international and domestic political rebuffs last year, the Reagan administration is pressing ahead with controversial proposals regarding chemical warfare - proposals that could have a broader arms control impact.
At disarmament talks in Geneva, US officials recently submitted a proposed comprehensive ban on chemical and biological weapons that would require tough, on-site inspection. This goes well beyond existing international agreements, which do not provide for independent verification of compliance.
At the United Nations, the United States is pushing for more international investigations of charges that the Soviet Union and its allies may be using outlawed toxic weapons in Afghanistan and Southeast Asia. US delegate Kenneth Adelman also recently pointed to reports that Soviet-supported Ethiopian armed forces are using chemical weapons against Eritrean rebels.
Here in Washington, the administration is urging Congress to approve $140 million for an upgraded US chemical arsenal that officials say is necessary to deter the use of such weapons by the Soviets in time of war. There is no doubt that the US is behind the Soviet Union in chemical warfare capability. But chemical weapons were one of the few things Congress cut from last year's Pentagon budget, and opponents are sure to fight them again this year.
The issue has important ramifications for the broader questions of arms control. Some key officials ask how the US and its allies can trust the Soviets on strategic and intermediate-range nuclear arms agreements (as well as conventional forces reductions in Europe) if, in fact, there has been violating chemical and biological weapons treaties.
At the same time, pushing forward on new controls in this area - despite the lack of strong interest and backing from other countries - is one way for the Reagan administration to show that it is serious about arms control. This was one of the messages carried to Europe by Vice-President George Bush recently.
Late last year, the first hard evidence of chemical and biological weapons use by the Red Army in Afghanistan and Soviet-supplied forces in Southeast Asia was disclosed by the US State Department. This included a Soviet gas mask contaminated with a yellowish powder identified as the mycotoxin associated with ''yellow rain,'' and autopsy results from Laos and Cambodia also indicating the presence of toxins.
While a UN investigating team had previously said it was ''unable to reach a final conclusion,'' it declared more recently that ''circumstantial evidence suggestive of the possible use of some sort of toxic chemical substances'' could not be disregarded. It also said a Soviet claim that toxic substances result from naturally growing fungi ''is unlikely to be valid.''
US officials have been frustrated by the slow pace and cautious conclusions of UN investigations, as well as by the lack of progress in US-Soviet bilateral talks on controlling chemical weapons.
For this reason, the US now is insisting - in an international forum - on strict verification of existing treaties and the destruction over a 10-year period of all chemical weapons stockpiles and production facilities.
''To sign agreements which lack tough verification standards would be not only misleading, but also a disservice to all who want real arms control,'' Undersecretary of State Lawrence Eagleburger told a Senate foreign relations subcommittee on arms control last week. ''The verification approach we have is tough, but fair and practical.''
At the same time, however, the administration wants to improve US chemical weapons stockpiles, which have not been added to since 1969, and which Army officials say are deteriorating. New weapons sought are ''binary'' artillery shells and bombs that do not mix poisonous chemicals until after they have been fired or dropped and are thus said to be safer.
Declared US policy is never to use chemical weapons except in retaliation for their use by others. The threat of such weapons forces opponents to don cumbersome protective gear that sharply degrades performance. The US must be able to force Warsaw Pact troops to do so, officials insist.