The Carter administration had notified Congress in secret that it intends to sell Iran seven highly sophisticated airborne radar systems for $1.2 billion.

This decision - which will be made formal and public July 6 - is expected to provoke the first public debate over American arms sale to foreign countries since President Carter announced a new policy intended to reduce those sales. Several administration officials said yesterday that the $1.2 billion sale to Iran violates that new policy, but others disagreed.

Two senators said they thought the sale flouted Carter's stated intentions, and Sen. Thomas F. Eagleton (D-Mo.) said it is "my very strong inclination" to introduce a motion in the Senate to block the sale.

The proposed deal - which was all but finally arranged by the Ford administration - raises many of the problems the Carter administration will face if it seriously tries to reduce America's role as an international arms merchant.

Opponents of the sale will attack it on many fronts, charging that it involves a radar system of questionable efficacy, that will escalate the arms race in the Middle East, that it risks revealing valuable secrets to the Soviet Union, that it could draw Americans in a future Iranian military adventure and that Iran is incapable of handling such sophisticated equipmemt.

Eagleton, a longtime opponent of this radar system, called the proposed sale "outlandishly incredible." Sen. John C. Culver (D-Iowa) said it was "basically contradictory to Carter's arms-sales policy."

Proponents reply that Iran has no reliable air defense system, and it is in America's interest to sell one to the shah. Because the system is primarily defensive, it should not escalate the arms race in the region. The fact that Americans will have to help man the system means the United States will be able to influence and restrain the shah if necessary, they add.

Administration officials also contend that the radar system - known formally as the Airborne Warning and Control System (AWACS) - is less lethal than many of the American weapons systems the shah would like to buy.

Since the Carter administration plans to sell the shah less than he was able to buy from the Nixon and Ford administration, they add, this sale should be seen as something of a sop to the Iranian appetite for fancy weaponry.

These officials note that Carter has already decided not to allow Iran to purchase F-18L fighter aircraft, a model that is unlikely to be built for the U.S. Air Force.

AWACS has long been a controversial system, and has already cost the United States more than $2.4 billion. For that amount the Air Force has thus far received two copies of the system - a modified Boeing 747 jet aircraft equipped with elaborate radar and data processing equipment built by Westinghouse.

Congress had appropriated funds for the gradual acquisition of 28 of them at a cost of $125.6 million apiece - more than the unit cost of the controversial B-1 bomber.

Two reports prepared by the General Accounting Office have sharply criticized the AWACS concept as extravagant and potentially ineffective. The GAO, an arm of Congress, is preparing another study of the implications of selling AWACS to Iran. It is also expected to be critical.

The original U.S. Air Force mission for AWACS was to provide a flying defense perimeter around the continental United States that would provide early warning of a Soviet bomber attack. As that threat diminished, the Air Force talked of using AWACS as a tactical weapon that could be used over a European battlefield.

Most recently it is described as most effective as an early warning system and potential command and control vehicle over friendly territory during an air attack, perhaps in Europe.

Through all these changes in proposed mission, the Air Force remained firm on one point: it needed 31 of the planes, whatever they were to be used for.

The United States has long been pressing its NATO allies to acquire an AWACS force for use in Europe. Though well-disposed to this idea in principle, the NATO countries have never produced the money to buy the expensive planes, and it is not clear that they ever will.

Congressional sources charged that the Air Force wants to sell AWACS to Iran in part to keep the project alive here, pending a decision by NATO to acquire it, or an increase in the number of planes acquired by the Pentagon. The Carter administration has reduced the annual U.S. "buy" from six to three AWACS planes - a level of production which Boeing officials call "not an economic rate."

The idea that Iran acquire AWACS is not a new one. It was most recently ratified in a study the Pentagon completed in January on a contract from the shah, who wanted U.S. advice on how to improve his air defenses.

According to one well-placed source, Westinghouse has a lot to do with preparing that report. "People in the Pentagon who reviewed that study got briefings on it from Westinghouse," the source said.

Carter administration officials cite that report as the justification for selling AWACS to Iran. The gist of its conclusions was forwarded to Congress in the advance notification of the sale - classified "confidential" - that the Pentagon sent to the Hill June 16.

The notification said a ground radar system would cost billions for Iran because of rought terrain and a typical air temperature patterns in the Persian Gulf, so AWACS was desirable. Moreover, the Pentagon said AWACS would enable Iran to guide fighter aircraft whose mission would be to defend cities and oilfields in case of an enemy attack.

This is a reference to the AWACS aircraft's acknowledged capability to serve as a command and control weapon - a defensive capability in an enemy attack, but potentially an offensive capability too, if Iran sought to launch an attack.

Culver and other critics cite this as the principal reason why the sale of AWACS to Iran would violate Carter's arms transfer policy.

In May Carter said that, henceforth, United States, would not be the first supplier to introduce into a region newly developed, advanced weapons systems which create a new or significantly higher combat capability."

For Iran's neighbors - Iraq, say - AWACS' command and control capability would certainly look like a new combat capability, Culver said yesterday.

Congressional critics also ask whether Iran can be trusted with AWACS' secrets (even its operating manuals are highly classified in the U.S. Air Force), and whether the United States wants to sell Iran a system that would admittedly hve to be manned by American technicians for years to come.

Each craft is intended to carry a crew of 26, according to one source, and most of these would be Americans until Iran's already-strained skilled manpower pool could be drawn on to provide native replacements.