Disturbing new evidence now under Carter administration study directly links the Soviet Union to radicals holding American hostages in Tehran, pointing to a strong Soviet hand in continuing the impasse.

These conclusions are contained in a confidential report on the National Voice of Iran, the clandestine Soviet radio. From transmitters located in Baku near the Soviet-Iranian border, NVOI puts out the real Soviet line -- exploitation by Moscow of the Iranian revolution to maximum U.S. disadvantage.

This new evidence shows a consistent Soviet campaign to undercut every settlement effort by President Abol Hassan Bani-Sadr and other Iranian leaders deemed slightly less hostile to Washington. Thus, this conclusion by U.S. experts: the Kermlin has its own agents inside the American embassy who are determined to keep the hostagae pot boiling as part of overall Soviet policy to gain eventual control of the Persian Gulf and its oil.

That suggests the futility of President Carter's alternating tactics of turning the other cheek to Iran or, as he did Monday, imposing sanctions. If the terrorists holding the Americans captive are taking orders from Moscow, the United States is actually confronting not a chaotic revolutionary regime but its fellow superpower.

"On the hostage issue," states a confidential report to Carter administration policymakers, "NVOI supports the position of the terrorist occupying the embassy, rather than those Iranians seeking some way out of the situation."

The official Soviet position, enunciated not long after the seizure last Nov. 4, put the Kremlin behind the rule of international law. But aside from that once-over-lightly support of the inviolability of foreign embassies, Moscow has done nothing to fortify the U.S. position. This silence has raised suspicions at high U.S. government levels that the Russians may have had an indirect hand in the embassy takeover. Now, they may be continuing to play that hand for the purpose of deepening Washington's humiliation.

Broadcasts in both the Farsi and Azerbaijani languages have been stridently opposed to Bani-Sadr and the so-called moderates in the revolutionary high command ever since they criticized the millitants holding the hostages. They accused Bani-Sadr, as economics minister, of giving tax concessions to "capitalists" and taking money from "toiling peoples' pockets."

That is just icing on the cake. The cake itself is the constant demand for ever greater "vigilance" (a routine catchword wherever Soviet power runs) and for regular purging of the revolutionary government, civilian and military. Bani-Sadr and his allies on the ruling Revolutionary Council, in other words, should be kicked out.

NVOI goes beyond mere purging. In its systematic undermining of the so-called moderates, NVOI demands that victims of purges should first be sacked and then "physically annihilated." U.S. officials are convinced that the Soviet target transcends remnants of the shah's old regime to include new "revolutionaries" who depart from the leftist and communits line.

"NVOI's repepated calls for a purge suggests that, like the Tudeh [communist] Party, it sees advantages for leftists and communists in additional turmoil in Iran," asserts the confidential report on NVOI's proganda line.

Preaching the gospel according to the Kremlin, NVOI mutes differences between Soviet policy and Ayatollah Khomeini's line -- such as Iran's attack on the Soviet invasion of Afghanistan. Appealing for Iranian support of the Afghan "nationlist" revolution, NVOI is lobbying hard for Iran to extend "the hand of friendship" to Kabul and stop support of Afghan rebels" along the Afghan-Iranian border.

The world of Islam, says the Soviet propanda, must follow the path laid down by Khomeini, not by Egyptian President Anwar Sadat. As for foreign friends, Iran's truest "natural ally" is the Soviet Union, followed by its Eastern European satellite states, Cuba, Syria and Soviet-dominated South Yemen.

The content of these broadcasts is not all that different from Soviet propaganda efforts through the years. What makes them notable is this ominous look into the future as planned by Moscow: turbulence from Pakistan to Turkey while the Kremlin consolidates it hold on Afghanistan and works to raise to power the most radical political elements in Iran. They surely include Moscow's friends inside the American Embassy.