Moscow — The Soviet Union has gone public with a new arms control proposal which a Soviet commentator says marks a ``serious step'' to bridge the positions of the superpowers. It specifically allows the United States to proceed with limited research into a Strategic Defense Initiative (SDI), the so-called ``star wars'' system, says Vladimir Chernyshev, a commentator on military and arms control issues for the Soviet news agency Tass. Previously, Soviet objections to SDI have been a major stumbling block in the Geneva arms control talks.
The new proposal was made public yesterday in a published account of a speech by Soviet leader Mikhail Gorbachev to a meeting of the Communist Party Central Committee. The meeting was held behind closed doors.
According to Tass, Mr. Gorbachev outlined the latest Soviet proposals at the Geneva talks. These included:
A limit for both superpowers of 8,000 strategic (long-range) nuclear warheads -- on a maximum of 1,600 delivery vehicles (``units'').
An agreement not to withdraw from the 1972 Anti-Ballistic Missile (ABM) Treaty for ``at least 15 years.''
An agreement to limit SDI research to ``laboratory tests.''
Separating the issue of medium-range nuclear weapons -- such as US and Soviet missiles in Europe -- from a comprehensive agreement on limiting strategic arms.
A Pentagon official in London rejected the proposal. The official, who asked not to be named, said that a large part of SDI involved experiments in space and that a restriction to laboratory research would thwart the program.
The exact numbers of warheads and delivery vehicles involved in the proposal were omitted from the Soviet press accounts of the Gorbachev speech, and were also dropped from several Tass accounts. That suggests that the issue is still a sensitive one within the Soviet Union.
Nevertheless, it marks the first time in recent years that a Soviet leader has publicly spelled out specific disarmament proposals that have been put forward at arms control negotiations.
The move reflects Soviet pique that the outlines of such proposals are routinely ``leaked'' to the Western press. Moreover, it is the Kremlin's way of responding to Western charges that it does not follow up public arms control initiatives with substantive proposals at Geneva.
Gorbachev said the proposals had been made at Geneva to facilitate ``the search for mutually acceptable solutions'' to disagreements over limiting nuclear missiles and preventing an arms race in space.
Mr. Chernyshev says the new proposals represent ``a very important concession and a move towards the US position'' at Geneva. Chernyshev, a retired Army colonel, often articulates the Soviet position on arms control matters. He was formerly a Soviet military representative at troop reduction talks in Vienna. His comments are the clearest indicator yet that the Soviets have modified their previously unqualified opposition to SDI.
Chernyshev said that ``General Secretary Gorbachev . . . is saying that the Geneva talks must move from deadlock.'' Previously, he said, the Soviet Union had resisted talks on space-based weapons or on weapons that could be used against targets in space.
``No discussions were even possible,'' he said, ``because we had decided not even to discuss SDI. . . . Now,'' he says, ``we agree on laboratory research on SDI.''
But a Western diplomat plays down the significance of the move: ``They [the Soviets] have already tested lasers [that could be used in an SDI system] outside the laboratory. So what are they talking about?''
Chernyshev acknowledges there is disagreement on what research is acceptable. But, he says, that points up the need to enter negotiations that would more precisely define the restrictions imposed by the ABM Treaty.
``This [new] proposal,'' he adds, ``is accompanied by a qualification that each side undertake not to go outside the framework of the ABM Treaty for another 15 years.''
But Western critics say that such an agreement would give the Soviet Union time to catch up with any US technological lead on SDI and would unduly inhibit Western research into space-based weaponry.
If the US would agree to the extension, he says, other disagreements could be resolved -- such as how to verify compliance with the ABM Treaty and the second Strategic Arms Limitation Treaty (SALT II) and how to verify reductions in nuclear missiles. And, he says, the thorny question of intermediate-range weaponry -- including missiles and forward-based bombers in Europe and Asia -- could be handled in separate negotiations.