The United States has turned down a request from Iran for 31 fighter-bombers fitted with the most sophisticated anti-radar electronic guidance system in the U. S. arsenal, the State Department said yesterday.

The request for the F4G aircraft and electronic missile guidance system known collectively as the Wild Weasel form part of a multibillion-dollar arms shopping list submitted by Shah Mohammed Reza Pahlevi early this year and now under active review by the Carter administration.

President Carter reportedly decided last week to reject the shah's request after intense debate within the administration, with the Pentagon favoring the sale and the State Department reportedly opposing it on the grounds that the technology was too sensitive to be given to another nation.

State Department spokesman Hodding Carter said yesterday that the administration has offered instead to sell Iran 31 F4E fighter-bombers and 1,000 Shrike missiles. The Iranians immediately agreed to purchase the missiles, but have not decided yet on accepting the offer of the standard model of the aging Phantom bomber.

The Shrike was described by officials as containing a more cumber-some and less reliable version of the Wild Weasel's electronic warfare capability, which locks on enemy radar emission frequencies, and then blinds and destroys the radar installation and antiaircraft missile batteries.

The United States has thus far refused to provide the equipment to any other nation. It has been in operational use by the U. S. Air Force for fewer than four years.

"We believe the Shrike missile will provide Iran with an appropriate capability for air defense purposes," Hodding Carter told reporters at the regular State Department briefing. "Understandably, the Iranians would have preferred the most advanced technology available."

During the Nixon and Ford administrations, the shah had virtually unlimited access to conventional U. S. weapons. Carter administration officials emphasized yesterday that the refusal was not aimed at Iran but resulted from the reluctance of the United States to export the sensitive technology involved in the Wild Weasel.

Last year, the administration approved the sale of an airborne warning and defense system to Iran and is still considering its current order for 70 F14 and 140 F16 fighters.