Soviet Foreign Minister Andrei Gromyko declared today that Carter administration proposals for strategic arms control rejected this week by the Kremlin represent a "cheap and shady maneuver" intended to give the United States an edge in nuclear strength.

Gromyko spoke at an extraordinary press conference, the first in years here by a top Soviet leader. It was called, he said, to respond to "rumors" that "distort reality" about the Soviet position in the talks with Secretary of State Cyrus R. Vance that ended yesterday in failure.

The press conference understood how wide the gap is now between Moscow and Washington on the neclear issue, which both sides regard as the crux of their relations. It demonstrated again the increasingly serious strain in superpower ties in these early months of president Carter's administraion.

"We shall be firm and resolute in defending our legitimate interests," Gromyko told reporters. "We intennd to conduct our relations with the United States on the basis of equality and only on that condition can we look into the future with optimism."

Responding specifically to assertions in recent days by Carter ad Vance that the United States had put forth in Moscow an innovative and "comprehensive" plan for steep reductions in nuclear weaponry, Gromyko said:

"The version widely circulated in the West alleging that the U.S. representative proposed a broad disarmament program at the talks in Moscow while the Soviet leadership failed to accept this program is basically false. Nobody proposed such a program to us."

Instead, Gromyko said in the course of a 90-minute largely extemporaneous discourse, the thrust of the Carter administraion propositions is to renege on the agreement reached in Vladivostok in 1974 between Soviet Communist Party chief Leonis Brezhnev and President Ford - which the Kremlin insists should be the basis for a SALT accord to replace the one that expires in October.

"What are we to do," Gromyko said, "if a new administration comes to office and throws aside what was positive that went before? We want stability in our relations. We would like them to be founded on the principles of peaceful coexistence and even better, that they should be friendly."

Gromyko assailed in detail the U.S. proposals given to Brezhnev in the Kremlin on Monday. He attacked both the one that Carter and Vance have described as sweeping in character and a narrower one that would amount to ratification of the Vladivostok terms, leaving aside for later negotiation the unsettled problems of controls on the U.S. cruise missiles and the Soviet Backfire bombers.

With a tone at times defensive and at times cutting, the foreign minister portrayed the Carter terms as unrealistic and even underhanded in thats they are meant to give the United States an advantage in strength.

"We shall not agree to retreat from the stand of equality," he said. "To strive for such a good is a cheap and shady maneuver."

The press conference - during Gromyko, in addition to his long speech, answered about a half dozen questions submitted in writing by reporters - was broadcast on Soviet television tonight, giving Russians a much more detailed accounting of the strategic arms megotiations of recent years than they ever had before.

The broadcast indicates that the Kremlin feels it necessary to persuade Soviet public opinion of its good faith in the bargaining at the same time that it wishes to dramatize its objections to the Carter proposals for foreign consumption. The Soviet leaders have so assiduouly procalimed the successes of detente politics and so often portrayed a SALT agreement as within reach that the sharp setbacks now evidently need to be carefully explained.

It is always possible, of course, that the Soviets mean their indignation to be a long-term negotiation tactic.

Gromyko casually disclosed aspects of the U.S. proposals that Vance in Moscow last night repeatedly refused to tell American reporters. He said that the United States wants to cut back the total number of missile launchers and intercontinental bombers on the two sides of 1,800 to 2,000 each, a cut of around 25 per cent from present levels. The number of missiles and bombers equipped with multiple warheads, according to Gromyko, would be 1,100 to 1,200. All of these figures are substantially below the ones agreed to at Vladivostok.

The United States, said Gromyko, is now suggesting "liquidation of our rockets that the U.S. doesn't like . . . They don't like them and that's all . . . What has changed following Vldivostok to require such a change? Absolutely nothing has changed."

Carter and Vance, in justification of their approach, have contended that the Vladivostok ceilings were so high that they did not represent significant arms-control measure, which their new plan would be.

Determinig the balance for whose argument is more correct is an extremely complex matter on which experts will no doubt be arguing until the issues are somehow resolved.

What seems most important at this stage is that, as Gromyko put it, there are "significant differences" on all phases of SALT now - and the Vance trip. Western analysts here generally agree, has created an impasse that at the moment appears unresolvable.

Gromyko's heavy stress today on negotiation stance suggests that this was the reason the talks broke down rather than Moscow's resentment over Carter's outspoken support of dissidents. Nonetheless, in response to a question, the foreign minister reiterated that "the so-called campaign in defense of human rights launched in the U.S. cannot but poison the poltical climate of relations between the two states and does not help in solving complex problems."

High-level party officials have been telling visiting Americans all week that the willingness here to compromise with the United States is sharply reduced by the extremely high level of irritation with the new administration.

Repeating what he told Vance at a luncheon yesterday, Gromyko said that Moscow is prepared to go its half way toward better relations with the United States. But "equal efforts are required on the part of the United States as well."