Imposition of tough economic sanctions against Iran by America's principal allies could cause short-term problems and prove potentially disastrous for basic Western interests in the long run, while benefitting the Soviet Union.

Besides prolonging the ordeal of the American hostages held here, imposition of sanctions by Japan and major Western European countries risks altering the predominantly Western pattern of trade and expertise here.

The main beneficiaries are likely to be the Soviet Union and its allies, according to informed Iranians and many diplomats here.

They fear an increased Kremlin influence and its potentially destabilizing repercussions on already shaky oil producers in the Arabian Peninsula.

These worries presume that a legacy of bitterness against any country applying sanctions would linger even if the hostages at the U.S. Embassy were released quickly.

So deep-seated are traditional Iranian suspicions of any foreign presence, it is argued, that smaller Western countries would be tarred with the same brush that has turned the United States into the symbol of rapacious predator here.

If Western Europe and Japan were lumped together with the United States, then Iran, in theory could turn to neutral or nonaligned states ranging from Switzerland and Austria to Yugoslavi and India.

But the sheer weight of Iran's needs -- in everything from spare parts and technology to trade intermediaries -- is considered to have a logic of its own involvement a massive Soviet bloc role.

Furthermore, the Soviet bloc provides a major potential outlet second-rate Iranian industrial production, which is not up to Western standards.Already Iranian textiles are being sold to the Soviet Union and Bulgarian sugar is replacing Western supplies.

Thus, the Soviet bloc would be poised to capitalize on its controversial economic investments made during the decade preceding Shah Mohammad Reza Pahlavi's overthrow a year ago.

The centerpiece was a Soviet steel plant exchanged for Iranian natural gas piped north across the border into southern Soviet republics. Also involved were Soviet military trucks and artillery while Romania, Bulgaria and Yugoslavia provided a wide range of equipment, tractors and other farm implements.

The West could be further hurt if Iran cut off oil sales to any nation applying sanctions, as oil Minister Ali Akhbar Moinfar recently threatened. a

With an estimated $8 billion in foreign exchange reserves -- not counting the funds frozen by the United States -- Iran is credited with the ability to survive for nearly a year even if it did not sell a drop of oil.

Ananlyst, however, believe Iran could sell its oil handily to Third World and other countries.

Looked at from the perspective of long term Western, and especially American, interests, sanctions paradoxically seem designed to undermine two basic policies: preserving continuous access to Iranian oil and maintaining Iran's suspicions about the Soviet Union, with whom it shares a 1,600-mile border and much bitter history.

"Here Iran is falling apart with provinces simmering with, or in full revolt, the economy far from recovered from two years of revolutionary disruption and revolutionaries in charge who couldn't care less about maintaining an industrial economy," one analyst remarked. "The West should be trying to get the economy going, reduce unemployment, which has cost one to two men out of five their jobs, and prevent the Soviets from making inroads."

Overlooking mounting American public pressure on President Carter over the hostages, many Iranians invoke similar reasoning to justify claims the United States is out to destroy the present government no matter what the cost.

Mindful of the large part that vengeance played in the first year of Ayatollah Ruhollah Khomeini's rule, one Iranian analyst remarked, "Two can play the revenge game, it would seem."

Such reasoning has reinforced the hard-liners. They argue that gestures toward Washington -- or what they construe as such -- only make the United States more intransigent. Exhibit A is Foreign Minister Sadegh Ghotbzadeh's timid -- and much criticized -- efforts to avoid sanctions to the United Nations.

Even he is now talking about the hostage's release in terms of months.

Feeding Iranian suspicions are memories of the C.I.A. role in toppling Prime Minister Mohammed Mossadegh from office in 1953 and puttng the shah back on his throne. That operation was made possible largely, because of Western economic sanctions that sapped his authority over the months.

But Iran in an oil-thirsty world is considered in a much stronger position to resist today and economic santions have proven notably unsuccessful elsewhere in the past quarter century.

"It's hard to bring Third World countries to their knees," a Western diplomat remarked. "They simply don't need the things highly industrialized societies must have on pain of collapsing. This is all the more true in Iran where the Westernized elite which was hooked on the consumer society, has left in droves or learned to live without Western goodies."

"Remember," he adfded, "from Khomeini on down, Iranian revolutionaries have been preaching the virtues of belt-tightening and self-sufficiency every since the embassy was seized in early November. Khomeini even led a five-day fast then to show the way."

Weighing the pros and cons of sanctions, a cynical analyst remarked, "They may be fine for Carter's election campaign, but it's hard to escape the feeling he's prepared to fight to the last drop of his allies trade."