Soviet Arms Pact Violations Listed : Reagan to Report Gains by Moscow; Reciprocal U.S. Buildup May Follow

President Reagan, in a report to be submitted to Congress on Monday, has concluded that the Soviet Union is making steady military gains and undercutting current arms control talks by persistently violating U.S.-Soviet agreements governing strategic nuclear weapons.

The report, coming at a time when Reagan is under pressure from the Kremlin to resume talks on a nuclear test ban, holds open the possibility that the United States may soon decide to make its own proportional pact violations as a hedge against Soviet military gains.

Discussed With Gorbachev

The President noted that he had discussed the violations with Soviet leader Mikhail S. Gorbachev when they met last month. Reagan said the violations “cause grave concern regarding Soviet commitment to arms control, and they darken the atmosphere in which current negotiations are being conducted in Geneva and elsewhere.”

According to Reagan, the Soviet violations are deliberate, persistent and designed to obtain a strategic advantage. “Through its non-compliance,” he said, “the Soviet Union has made military gains in the area of strategic offensive arms as well a chemical, biological and toxin weapons.”

Despite the recital of Soviet violations, nowhere in the report did the President threaten to cancel any existing arms control agreements. He noted that the Pentagon is still working on recommendations that he requested last June on possible retaliatory violations by the United States.

Pentagon officials said their report has been delayed by a disagreement within the Defense Department over the recommendations. Among other things, the report is expected to call upon Congress to lift the current self-imposed limit of 50 on the number of MX missiles to be deployed by the United States.

Nine cases of Soviet violations were cited in Reagan’s unclassified report, a copy of which was made available to The Times and several other news organizations. Many of the alleged violations were detailed in previous Administration reports to Congress.

The most important new evidence outlined in the report relates to Soviet deployment of SS-25 intercontinental ballistic missiles during 1985, which the President portrayed as a violation of the unratified 1979 SALT II treaty. Although SALT II officially expires on Dec. 31, both superpowers have said that they will continue to abide by it.

The Soviets contend that the SS-25, a mobile missile that can be modified to carry more than a single warhead, is permitted under the treaty.

Spring Decision Planned

Last week, Administration officials said they have decided to postpone until next spring a decision on whether to continue complying with the SALT II treaty. If officials then decide to begin sea trials of a new missile-firing Trident submarine, they will be forced to either exceed the limits of the treaty or to dismantle two Poseidon submarines.

The report also publicly charged for the first time that the Soviet Union has exceeded the level of 2,504 strategic nuclear delivery vehicles, such as missile launchers and heavy bombers, contained in its arsenal at the conclusion of the SALT II treaty.

It also said the Soviets have recently begun to undercut treaty compliance by violating a ban on deliberate concealment of nuclear testing measures.

Reagan renewed earlier charges that the Soviet Union has violated the 1972 Anti-Ballistic Missile Treaty by building a new radar facility near Krasnoyarsk in Siberia, which could be used as part of a national defense against incoming missiles. He said it proves that the Soviets “are capable of violating arms control obligations and commitments even when they are negotiating with the United States or when they know we will detect a violation.”

SALT I Violation

The Soviets also were accused of using dismantled SS-7 missile facilities for the SS-25 in violation of the 1972 SALT I treaty. In addition, the report charged that the Kremlin has probably exceeded the 150-kiloton limit on underground nuclear testing and permitted some of the underground tests to vent into the atmosphere.

At the same time, the report cited several instances in which the Soviets appear to have corrected past violations. These include lowering the production rate of Backfire bombers to below 30 per year and cutting back on the use of lethal chemicals in Cambodia, Laos and Afghanistan.