The Soviet government sharply criticized President Reagan's "new approach" for dealing with Moscow tonight as a public-relations ploy obscuring his intentions to maintain East-West tensions and seek military superiority over the Soviet Union.

In the first authoritative response to Reagan's speech on East-West relations Sunday, the official news agency Tass said the president's conciliatory tone masked the confrontational substance of his policy.

The commentary, which the Russian-language Tass wires headlined as "Tass statement" to indicate that it reflected the official Kremlin view, made only a passing reference to Reagan's call for the start of talks on strategic arms as soon as next month and did not even mention any of the issues due to be negotiated.

This underscored the impression created by the Soviets yesterday that they had great reservations about Reagan's arms reduction proposals but that they would not reject his offer to resume strategic arms reduction talks.

Instead, Tass tonight launched a broad attack on the president's overall approach to the Soviet Union, saying his speech combined "fabrications" about Soviet intentions and "trite assertions about Soviet aggressiveness and buildup of the Soviet military might."

It charged that Reagan was pressing U.S. allies to reduce trade with socialist countries to a "minimum" and that he was seeking to "encourage worldwide processes directed against the interests of socialist countries."

"Remarks scattered throughout the text of the speech--about the aspiration to preserve peace at present and in the future and readiness to establish new understanding with the Soviet Union--were evidently needed by the president for camouflage and present in a more effective way as a 'constructive step' the announcement that the United States, after 18 months of delays, finally decided to start talks on strategic armaments.

"The lengthy explanations by which the president accompanied his announcement, however, show that in fact constructiveness is not even thought about in Washington.

"The U.S. leadership is being driven by the same idee fixe, namely to achieve unilateral advantages and damage the security of the Soviet Union and its allies."

The commentary singled out what it said was Reagan's stated objective of the decade, to secure "genuine and long-term limitation of Soviet military programs." It said the United States did not make "corresponding pledges."

The timing of his speech reflected Reagan's attempt "to abate the wave of antiwar demonstrations in the United States and Western Europe" prior to the NATO summit next month and "at the same time to exert pressure on the U.S. allies."

Tonight's Tass statement was seen by observers here as Moscow's first propaganda salvo in the polemics expected to surround the anticipated resumption of U.S.-Soviet strategic arms negotiations.

The Soviets appeared annoyed by Reagan's public disclosure of specific proposals on reducing each side's strategic arsenals. His easy-to-grasp formula and assertions by his aides that he wanted to establish a constructive dialogue with Moscow are seen here as clever moves to disarm antinuclear groups in the United States and Europe.

Significantly, however, the Soviets have not yet published the specific proposals by Reagan. Tass yesterday gave a preliminary list of Soviet reservations about various aspects of his plan, but did so by quoting Western and specifically American critics of the president.

This suggested that Moscow is seriously studying the proposals and that it may come up with an alternative package of ideas for the forthcoming negotiations.