Moscow — Even while wooing Iran, the Soviet Union has begun hinting at a much tougher approach should the Iranians not reciprocate. The Kremlin seems particularly concerned over Iran's persistent and vocal condemnation of the Soviet military presence in Afghanistan, and by the recent resolution of Iran's hostage stalemate with the United States.
The Soviets are making it clear that they view a reliable relationship with Iran, their unstable southern neighbor, as one important counterweight to a buildup of US military strength in the Gulf region.
It is against this background that the USSR has been energetically wooing Iran, despite clear signs of reluctance from that country's dominant Muslim fundamentalists.
With the same concerns in mind, Moscow has conveyed two stern messages to the Iranians in the past month.
The more recent one, carried in the Soviet government newspaper Izvestia, is described by a diplomat here as "amounting to an implicit threat" of a tougher Soviet policy toward Iran.
What, specifically, the Kremlin may have in mind remains unclear.
Yet both Western and third-world diplomats here say there is no doubt the Soviets still consider valid a 1921 treaty with Iran allowing them to intervene in that country militarily under specified circumstances. The Iranians unilaterally abrogated that provision in their ardor for militant nonalignment after the revolution.
The diplomats, moreover, point to three major potential sources of Soviet leverage over Iran:
* Direct influence over the small but tightly organized Tudeh (Communist) Party inside Iran, which has generally sided with the dominant fundamentalists in that country's bitter internal power struggle.
* Physical proximity to some of Iran's restive ethnic regions, such as Azerbaijan and Kurdistan. The Soviets backed brief breakaway governments in that area after World War II.
* The ability to influence Iran's war with Iraq by resupplying the Iraqi's largely Soviet-equipped forces.
Moscow so far has insisted on strict neutrality -- no doubt partly in hopes of impressing Iran, and partly because relations with one-time Arab petro-pal Iraq had not been too good of late, anyway.
The Soviets do clearly hold out some hope their diplomatic overtures toward Iran may yet bear fruit.
An Iranian cultural delegation visiting Moscow to mark the second anniversary of the Iranian revolution found itself sounded out on Soviet proposals for Indian Ocean detente, the official Moscow news media indicated.
When the delegation leader, fundamentalist and one- time Iranian presidential candidate Jelaloddin Farsi, publicly knocked the Soviets' lack of support for Iran in the Gulf war, those remarks went delicately unreported by the Soviet press.
Iran's ambassador was allowed to address Soviet television viewers on the anniversary of the Iranian revolution, the kind of recognition usually reserved for states the Soviets want to court.
But there have also been signs of toughness.
In mid-January the Iranian ambassador was handed a protest over the late-December assault on the Soviet Embassy in Tehran by opponents of the invasion of Afghanistan.
The Soviets had already protested once. The presentation of a second, tougher note two weeks later was seen by diplomats here partly as an indication its message transcended the single incident and was meant to be read painstakingly in Tehran.
The note accused the Iranians of cottoning up to those who attacked the embassy. Moscow threatened that if Iranian authorities either could not or would not protect Soviet institutions and citizens in Iran, the USSR would do so , itself.
The second signal to Iran, diplomats argue, came in a Feb. 10 commentary in Izvestia commemorating the Iranian revolution.
The article rapped the country's post-Shah leadership for economic and social mismanagement, adding tartly: "The [ethnic] nationalities question has not been solved on a democratic basis."
The commentator went on to detail Soviet cooperation with Iran, concluding: "In its turn, the Soviet people has the right to expect of Iran a friendly and good-nei ghborly attitude."