The on going political and social unrest in Iran that has left the local economy largely paralyzed is threatening to jeopardize a vast multi-billion-dollar construction program by several major Italian state companies and scores of smaller private concerns.

The extent of Italian involvement in the Iranian economy is substantial, equal to one third of all its contracts with third world countries and thought to amount to over $6 billion. The 12,000 italians in Iran, who represent the lrgest group of foreigners after the 40,000 Americans, have so far avoided becoming a major target for anti-Western feeling.

But the moralization program put into effect by the current military government has already resulted in the arrest of one Italian businessman.

And this development, as well as a reported delay in payments, shipments, and oil consignments is causin deep concern here, particularly at "IRI," the giant state holding company.

Two of this giant holding company's firms have already spent millions of dollars on Iranian construction projects and could risk huge losses if the shsh should eventually be overthrown or step down.

Current Italian contracts in Iran date back to the June 1974 economic cooperation agreement worked out by the two countries. The following years saw a flurry of business negotiations, the major outcome of which were cotracts by two "IRI firms, "Le Condotte D'Acqua" and "Italimpianti" for the construction of a giant port and steel complex at Bandar Abbas.

Other major projects include the world's highest pipeline, being constructed by two Itlian firms, "Snam" and "Saipem", 400 kilometers of road undertaken by "Italstradec along the Afghanistan-Pakistan border, $50 million worth of schools being built by "IPI", contracts for $500 million worth of helicopters built by "Agusta", and a huge dam under construction North of Teheran by "Impregilo".

Financed by the Italians with contractural provisions for gradual repayments, many of these firms have been adversely affected by the chaos and strikes in Iran that has closed banks, ministries, and local suppliers.

Furthermore, according to reports from Teheran, totl credits due the Italians currently amount to over 240 million dollars.

"Italimpianti" has so far received only 15 percent of its investment of $1.5 billion, and in recent months the Iranians have fallen sharply behind in the payment of $30 million worth of crude oil. Over $20 million is owed "Italstrade" the "Gruppo Industrie Electtromeccaniche" (GIE) is waiting a payment of over ten million dollars, and "Impregilo", is also reportedly having serous problems.

The hardest hit company however, appears to be the "Condotte" which is now owed between $140 million and $180 million by the Iranian government. According to officials of the company, who say stopping work would be more costly than continuing it, the Iranians have promised to pay as soon as possible what they owe on Condotte's 1.1 billion dollar costruction plan.

The "Condotte" firm has also run into problems at home because of the recent arrest in Teheran of Lucio Randone, the general manager of the "Condotte-Mahestan" company set up with the Shah's sister in April 1977 for the construction of 1500 luxury apartments on a 37,000-square-meter lot north of Teheran.

Irregular dealings by Iranian administrators and illegal capital export culminated, following Princess Ashraf's flight abroad in November, in a series of arrests, including that of Randone. This has set off charges of corruption against "Condotte" officials although insiders say the deal was a small one and served the company primarily as a chance to get on a good footing with the powerful Pahlevi Foundation run by the Shah and his family.

It has also led to mini-brouhaha at home, with the minister of state economic participation, Antonio Bisaglia, publicly demandinf the resignation of "IRI Chief Alberto Boyer for his apparent failure to formally inform the minister of the "Condotte-Mahestan" merger.

Furthermore, the problems encountered by the two "IRI" companies has led to charges here that hasty decision about Bandar Abbas may now threaten IRI's solvency. Officials of the companies have responded to these accusations by defending the economic validity of their Iranian contracts and expressing guarded optimism that any eventual change in regime in Iran would not necessarily be prejudicial to Italian interest.

"IRI" officials here believe that any Iranian government will want work on the port and steel complex to continue.

"Our minds are at ease because the work we are doing is valid from the economic point of view," Italimpianti General Manager Lucien Sicouri told the Milan daily "Corriere Della Sera" earlier last week.

Sicouri explained that whereas today Iran imports six million tons of steel each year, when the Bandar Abbas plant is completed it will be able to produce 2.5 million tons on its own. "No government will be able to question this project, because it is essential for the economy of the country," he added.

He was echoed by Loris Corbi, president of the Condotte, who insists that up until now the port project has been given "absolute economic and social priority" by the Iranians. "We believe, therefore, that whatever happens the contract will be carried through."

Nevertheless, recent threats from Paris by the Shah's chief opponent Aytollah Ruhollah Khomeini that foreign contracts signed by the Shah's regime would be considered null and void by an islamic government are worrisome.

Although Italian firms working in Iran have so far avoided attack from xenophobic anti-Shah Iranians, there have been some disturbing incidents. In November the cafeteria of a "GIE plant in Isfahan was burned down and in early December a construction yard of an Italian electric company was attacked.

Even more disturbing was the assault earlier this month by a mob of about 100 persons on a "GIE dormitory in Bandar Abbas. According to one foreign trade expert, "it is these kind of incidents, more than the payments delays that have occurred so far, that create concern for what could happen in the future."