Assessing the growing conflict over the Reagan Administration's sale of arms to Iran, Harvard professors in a variety of fields said that the affair would severely undermine U.S. interests abroad.

They also questioned whether the president will be able to regain his influence with Congress or restore his standing with the American people.

Experts in foreign relations said revelations about the Iranian connection dealt a crushing blow to the credibility of U.S. foreign policy toward the Middle East, Europe, Central America and the Soviet Union.

Regarding the impact of the crisis on relations in the Middle East:

Scholars said the international crisis threatens to destabilize moderate regimes in the Middle East. The involvement of prominent Saudi Arabians andpossibly members of the Saudi government in thearms transactions may cause a backlash againstSaudi Arabia in the more radical Arab world,scholars said.

Professor of Social Anthropology and MiddleEastern Studies Nur O. Yalman called the situation"very dangerous." Yalman said that Saudi Arabia is"isolated and vulnerable to attack from extremistfactions" as a result of its cooperation withIsrael and the U.S. in the sale of arms to Iran.

The governments of other Middle Easterncountries may also be in jeopardy, he said. Yalmansaid the "effect on the moderate governments inthe Middle East, including Saudi Arabia, Jordanand Egypt is the worst aspect of the arms sale."

Yalman criticized what he called a lack ofcontinuity in American foreign policy by saying,"United States foreign policy toward the MiddleEast has been conducted on a day-to-day basis."

Professors also challenged the Administration'smain justification for the Iranian arms deal.

President Reagan said his aim was to establishties with moderate elements in Iran, but oneMiddle East expert said there are no such elementsthere.

Laurie Mylroie, a government instructor andassistant director of the Center for MiddleEastern Studies, said that what is left in Iran is"a revolutionary core" and that the Americangovernment was "working with the Khomeini regimeand not a moderate faction."

"It's pretty absurd to think that there aremoderates in Iran," Mylroie said.

Regarding the impact of the crisis onrelations with Europe:

"Along with the failure of the ReaganAdministration at Iceland, this crisis deals ahideous body blow to European enthusiasm forAmerican leadership," said Dillon Professor of theCivilization of France Stanley H. Hoffmann.

Hoffman said the European reaction will be oneof "general dismay."