U.S. Offers Earlier Date for Stopping Poison Gas Output : Chemical arms: Baker hopes to wrap up details during talks in Moscow next week.

In an effort to resolve a key impasse before the superpower summit in three weeks, the Bush Administration has offered to move up the date for ending poison gas production as part of a proposed U.S.-Soviet chemical weapons treaty, officials said Tuesday.

A senior State Department official said Secretary of State James A. Baker III hopes to wrap up details of a chemical weapons pact when he visits Moscow next week for talks with Soviet Foreign Minister Eduard A. Shevardnadze. A reply to the U.S. offer is expected at that time.

The U.S.-Soviet poison gas agreement is thought to be much closer to completion than any other arms control pact now under consideration by the two countries. President Bush and Soviet President Mikhail S. Gorbachev have made it clear that they want to sign at least one arms control treaty at their May 30-June 3 summit in Washington.

Another official said the Administration is ready to compromise on its earlier insistence that the United States continue to produce modern chemical weapons until all nations capable of manufacturing war gases agree to a global ban.

The official said the exact date for ending production remains to be negotiated. But non-government experts said that the Administration appears ready to end production either within three years or when the U.S.-Soviet agreement takes effect.

The new proposal is intended to remove a Soviet objection to a plan outlined by Bush in a speech to the United Nations last September calling for the United States and the Soviet Union to begin at once to destroy most of their existing stockpiles of chemical weapons.

Bush suggested that both nations cut their arsenals to 5,000 tons. That would reduce the U.S. arsenal by 80% and the Soviet arsenal by about 95%. Moscow accepted the Bush proposal in principle but insisted on an immediate end to U.S. chemical weapons production.

The United States originally wanted to continue production so that the 20% remaining after the cuts would consist entirely of modern binary weapons--chemicals that only become deadly when combined. Such weapons are safer to store than the existing stocks of poison gases.

Another potential obstacle to the chemical weapons agreement, however, is a Soviet schedule for destruction of its chemical weapons stocks.

The United States could begin destruction in about a year at eight facilities. In contrast, Moscow has only one such facility, which is now inoperative. The Soviets contend that destruction at the pace proposed by the United States would be unsafe.

In a related development, Soviet Marshal Sergei F. Akhromeyev denied Tuesday that Moscow has backtracked on earlier concessions in talks on reductions of long-range nuclear weapons and has jeopardized early completion of the strategic arms agreement.

Akhromeyev, who is Gorbachev’s chief arms control adviser, told a Senate Armed Services subcommittee that Moscow’s position on sea-launched cruise missiles (SLCMs) is consistent with a statement at the U.S.-Soviet 1987 summit. The statement committed the two nations to establish ceilings on these weapons that could be verified if possible.

U.S. officials believed the Soviets had moved away from that demand in February, however, by agreeing to deal with SLCMs by issuing “politically binding declarations.” But last month, the Soviets returned to their demand for ceilings, which connote legally binding limits, and with verification provisions.

“We’re not backtracking,” Akhromeyev insisted. “We are pushing both statements. We’re still prepared to confirm (SLCM force size) in parallel, politically binding declarations. But they (the declarations) must limit deployment. If not, the (strategic) treaty could be bypassed with deployment of many thousands of SLCMs. The treaty would be nonsensical.”

The Pentagon had planned to build about 4,000 long-range SLCMs, most of them conventionally armed but about 750 with nuclear warheads. The Soviets have proposed a nuclear ceiling of half that amount.

The primary purpose of Akhromeyev’s visit was to explain Moscow’s longstanding call for new negotiations to reduce tactical nuclear arms, including cruise missiles, torpedoes and depth charges carried by ships and submarines at sea.

Akhromeyev warned that these tactical nuclear arms “are less protected” against unauthorized use than the nuclear weapons of the other armed services “because of unavoidable autonomous sea patrols of every ship carrying out training-combat tasks.”

Akhromeyev appeared to be suggesting that because ships operate far from port and reliable communications, naval commanders have greater authority to use nuclear weapons.