The Defense Department, which last year persuaded Congress to end a 16-year U.S. moratorium on production of nerve gas, wants money for research on a new generation of chemical weapons, a Pentagon official told Congress yesterday.

The Pentagon also seeks fiscal 1987 funds for development of a new rocket warhead capable of carrying chemical weapons deep behind enemy lines. After years of resisting requests from the Reagan administration, Congress has approved production of a 155 mm artillery shell and the "Bigeye" bomb to carry "binary" nerve gas, which is touted as safer than current stockpiles because its chemicals are supposed to remain separate and inert until the weapon is fired.

The Pentagon in fiscal 1987 would like $25.3 million to develop the chemical warhead for a rocket known as the Multiple Launch Rocket System (MLRS) and $12 million to begin research on "novel lethal and incapacitating compounds," Thomas J. Welch, deputy assistant secretary of defense for chemical matters, told a Senate Armed Services subcommittee.

Stressing the need for systems that will "incorporate greater range, greater accuracy and stand-off capabilities," Welch said that "a long-range master plan for future development of retaliatory systems is among the projects which will ensure our future chemical systems are survivable, readily usable and affordable."

Sen. David H. Pryor (D-Ark.), an opponent of the chemical-arms program and whose state will produce the binary weapons, said, "It's outrageous they would come in with a whole new program when the current program has hardly begun.

"We have whetted the Pentagon's insatiable and unending appetite," Pryor said. He added that he is amazed at "how they are thinking up new ways kill people."

The Reagan administration has argued that the United States must modernize its chemical stockpile, much of which is stored in West Germany, in order to make the arsenal safer and a deterrent against extensive Soviet chemical warfare capabilities.

At the same hearing yesterday, it was disclosed that the United States has rejected a suggestion by the Soviet Union for a nonproliferation treaty on chemical weapons.

David F. Emery, deputy director of the Arms Control and Disarmament Agency, told the subcommittee that "we feel a formal treaty. . . [would be] inappropriate" because it would "detract from the achievement of a global ban" on chemical weapons. Emery described Soviet leader Mikhail Gorbachev's initiative as "a positive step, since it showed Soviet concern about [chemical-weapon] proliferation."

Meetings between superpower representatives last month in Bern, Switzerland, on curbing chemical-weapon proliferation, Emery said, dealt solely with explanations of export controls by each side. However, the United States made it clear that nonproliferation "should not be allowed to interfere with negotiations on a complete ban," he added.

Emery said that congressional approval last year of production of binary chemical weapons had renewed Soviet interest in discussion of a ban.

Nonetheless, he said, Washington remained "unsatisfied with the slow pace of negotiations."

The proposed U.S. chemical treaty presented at Geneva would allow the United States "to inspect any relevant facility in the Soviet Union or elsewhere that was of concern to us," Emery said.

NATO governments have begun the process of approving U.S. production of binary weapons, as required by the legislation passed last year as a condition for resumption of chemical-weapons production, according to David Abshire, U.S. ambassador to NATO.