THE UNITED STATES has an economic stake in Iran that goes beyond the oil this country buys there. The American interest comprises billions of dollars of construction and service contracts, investments in factories and office facilities there, and a sizable volume of exports and sales of military equipment.

The totals include:

$3.8 billion in American exports to Iran each year, ranging from agricultural products and consumer goods to heavy industrial equipment.

$2.6 billion or more in military sales to the Tehran government, including some of the most sophisticated U.S. planes and weaponry.

$700 million in direct investment by U.S. firms in factories, offices and construction facilities in virtually all parts of Iran.

41,000 Americans now living in Iran, including families of U.S. workers.

The oil problem is the most acute, of course. While the cutback stemming from the recent strikes has been made up by Saudi Arabia, there's no doubt the Iranian strikes have bolstered the hand of more hawkish oil-producing nations that are pushing for a larger prise rise at January's meeting of the Organization of Petroleum Exporting Countries.

Forecasts are that the January price boost, which was expected to reach only about 5 percent, now is likely to be closer to 10 percent. The larger the boost in oil prices, the more it could hurt the U.S. economu and deepen the trade deficit - developments that would further depress the dollar, which has been declining in part because of excessive U.S. import costs.

But the impact on oil prices is only one of the economic consequences the present crisis is expected to bring. Analysts say that even under the best circumstances, Iran cannot escape domestic eruption.

The Iranian economy already has been dealt a blow by last week's strikes. Reduced oil production has cut revenues by $1.5 billion. Inflation seems out of hand.

The question is: How much will the current political crisis disrupt this flow of sales and construction programs, even if the Shah is successful in quelling the rioters? Although it's still too early for analysts to assess the damage, there's general agreement that the turmoil can't help but slow the pace of Iran's economic activity. The only issue is how much.

There were signs even before the latest disorder that the Iranian economy was slowing from the post-1973 oil boom and that the government would have to cut back sharply. Even before the strikes occured, real growth was estimated at a relatively minuscule 2 percent - far below last year's 13 percent growth, and a visible comedown from the 20 percent pace experienced earlier.

The shah already had had to scrap one major industrialization program, and was preparing to postpone another when the rioting began. Indeed, some analysts say the reason the Moslems were unable to draw so much sympathy from other Iranians had more to do with the country's growing economic squeeze than with the shah's internal politics.

U.S. analysts already are predicting the Iranians will have to delay or scale back dozens of big economic projects, including steel mills, nuclear power plants and petrochemical complexes, and several key military programs also may be killed. The changes will affect major West German and Japanese firms as well as American companies.

Completion of the Arymehr International Airport, just south of Tehran, now may be postponed beyond 1985, and the $2-billion Chah Bahar naval base, bordering Pakistan, may be scrapped altogether. Also likely: delays in construction of new steel mills, such as the $800-million project Kaiser Engineers is preparing to build at Ahwaz.

The slump in the Iranian economy also is expected to cut into the bustling U.S. export market there which has burgeoned in recent years in the face of the government's stepped-up efforts to speed industrialization with Joan's new-found oil revenues. American exports to Iran reached $2.7 billion last year - about 2 percent of total U.S. exports.

This year, trade officials had expected U.S. sales to Iran to total $3.8 billion - mostly in food, consumer goods, machinery, aircraft and transportation equipment - with an even larger export volumes likely in coming years as the country complete its industrialization process. But experts say the political strife could trim U.S. exports there as much as 10 per cent.

Moreover, the impact on U.S. economic interests doesn't stop with exports. Commerce Department figures show more than 500 Americans companies have permanent plants in Iran, with a massive equity investment of $700 million. And that doesn't include contracts for short-term technical help. In all, there are some 41,000 Americans based in Iran for business ventures.

The list includes some of the largest U.S. corporations. Bell Helicopter has an assembly and repair facility in Isfahan. DuPont is building a chemical plant there. General Motors has a factory turning out Cardillacs, Buicks and Chevrolets. John Deere builds tractors there. And dozens of construction firms are involved in projects.

There also is a hefty package of U.S. military sales to Iran each year - with some $12 billion worth of equipment now on order from American arms makers. New contracts from Iran for American military goods reached $2.6 billion this past fiscal year, following $5.8 billion in purchases during fiscal 1977. Since 1973, it's totaled $19 billion. A Fading Dream

ANALYSTS say about the only economic gainers in the entire affair may be exporters of agricultural equipment. In the wake of the recent disorders, any revamped government is almost certain to place more emphasis on bolstering family farm operations.And Iran may seek to build more rural-urban roads to get farm products to market more quickly.

Whatever the political and strategic outcomes of the current crisis, it's clear that, at least as far as the economic issue is concerned, the disorders that closed Iran's oil pipelines this past month also choked off the cornucopia that Iranian officials - and many U.S. firms - saw after the 1973 price increases.

The quadrupling of oil revenues then, and the increase during the ensuing years, led to a vision of Iran as an economic boom town and to dreams by the shah of a rapid move forward from another Middle East desert-nation into a modern industrial state. That dream had been fading earlier, but now it seems to be disappearing more quickly.

In any case, the result will mean a new round of problems for the United States and for American companies operating in Iran - which some fear could blunt further new investment there, if not discourage existing operations. While most U.S. firms have limited their exodus to removing dependents, executives are watching the situation carefully and dusting off long-shelved contingency plans.

"We haven't tried any wholesale evacuation, but we have taken out some dependent children in a few sensitive areas," says O.C. Roddey, executive vice president of the Ralph M. Parsons Co., a Pasadena-based construction firm with 600 employees and family members in Iran. "We try to keep in touch daily," he says. "The difficulty has been to get through by phone."