The Soviet government newspaper Izvestia tonight declared that the United States "is regarded in Iran as the main foreign mainstay of the anti-popular regime" and denounced "a demonstration of force directed against the Iranian people" by U.S. Navy ships it said were steaming toward the Persian Gulf.

The commentary followed by one day an official U.S. complaint to the Soviet Foreign Ministry over a similar commentary in the Communist Party newspaper Pravda. That article, viewed by Washington as "inflammatory," asserted that the United States has sent a "political and intelligence team" to Iran in an effort to influence Iranian developments.

Moreover, Izvestia tonight asserted that U.S. warships were moving toward the Persian Gulf despite the fact that President Carter had let it be known Tuesday that he had reversed himself and had ordered the vessels not to proceed from the South China Sea toward the Middle East.

The Izvestia article showed anew that the Russians are edging away from support of the shah in his struggle to stay in power in his strife-torn strategic nation. And it demonstrates the government's deep concern that American millitary power could be used to bolster his pro-Western government despite Carter's pledges to the contrary.

"It is an objective fact that the popular movement in Iran has assumed anti-American overtones," Izvestia said. It asserted that the United States, "strivin to safeguard its posicombines demonstrative navy maneuvers with economic means of pressuring, with political machinations within Iran prompted by advisers from the CIA and other U.S. specail foreign services stationed in Tebran."

Ezvestia claimed that the formation of a civilian government by Shahpour Bakhtiar constitutes "one such sttempt to turn the tide of events."

Diplomatic sources here point out that the Soviest, while resorting to commentaries in Izvestia and Pravda to show the government's careful recent hedging against the shah after tacit support when his troubles began last fall, have not yet issued a definitive analysis of their position on the turmoil in Iran, a key neighboring state. While critical of the United States, official media accounts have not named the shah directly.

The Soviets, meanwhile, have increased Persian language broadcasts into Iran critical of U.S. activities there.

"They're tilting, exciting more and more people in Iran," commented one Western source. But, he added, the Soviets have not come out yet to say what may be on their minds.

Western sources here maintain there is no evidence of active Soviet maneuvering within Iran against the shah or on behalf of his adversaries. But the Persian language broadcasts from the Soviet Union are clearly directed toward that end.

In Novermber, Soviet President Leonid Brezhnev issued an abrupt warning to the United States against military interference in Iran, saying it "would be regarded by the U.S.S.R. as a matter affecting its security interests."

Iranian oil shipments to the United States have been interrupted, and its substantial natural gas flow to Soviet Industries in the Trans-Caucasus also has been sharply cutback. Izvestia said Iranians consider the United States "as a power which foisted the policy of militarization upon the country, as the state of the monopolies that have seized a considerable share of Iran's natural resources. Washington always looked upon Inan as its main beachhead in the entire oil-bearing area adjoining it."

Meanwhile tonight, the Soviet news agency Tass reiterated a recent standard Soviet formulation that the United States had forced heavy military spending upon Shah Mohammad Reza Pahlavi while foregoing social expenditures improve the lot of Iran's masses.

It added that the United States is now attemption to "distract attention from their interference in that country's internal affairs" by using "hackneyed slanders against the Soviet Union. They are trying to lay the blame at the door of the U.S.S.R., alleging that it si fomenting anti-American sentiments in Iran. Facts indicate the contrary."