U.S. military personnel and civilians working for defense contractors would play an important role in a Saudi Arabian AWACS program for as long as the sophisticated radar planes were in operation, a senior White House official said yesterday.

Initially, 30 U.S. Air Force personnel and about 410 American civilians hired by Boeing and other defense contractors would be needed to fly, operate and maintain the complex planes, according to the White House official. But it remains to be decided just what their role and their orders would be when the Saudis took title to aircraft surveillance planes, the official said.

Statements by the White House official in a background briefing for reporters were among several elements of an emerging Reagan administration campaign to make its case for the controversial arms sale. In other efforts:

Secretary of State Alexander M. Haig Jr. and Secretary of Defense Caspar W. Weinberger met at the State Department with 30 leaders of American Jewish organizations, which have vowed to seek congressional disapproval of the arms sale package. Haig, according to a participant, asked the Jewish leaders to "keep your powder dry until you see the bottom line" of final arrangements to be made by the United States with the Saudis.

The visitors appeared to be unconvinced. Howard Squadron, chairman of the Conference of Presidents of American Jewish Organizations, said after the meeting that a full-scale lobbying campaign would be mounted against the proposed sale, and he estimated that Congress would block it if the vote were today.

On the issue raised by the White House briefing, Squadron said Jewish groups would be less opposed is U.S. personnel were "an indispensable part of the package or if there were some other American string on this weapons system." But he added that he understood that "the sale is an absolute sale and they [the AWACS planes] will eventually be in the hands of the Saudis totally."

State Department spokesman Dean Fischer outlined the core of the administration's case that the sale of AWACS (airborne warning and control system) to Saudi Arabia "would not constitute a realistic threat to Israel."

Among the reasons given by Fischer were that AWACS "will have no radio monitoring, photo-reconnaissance or intelligence-gathering capabilities" and cannot detect militarily significant ground activity; that it cannot be used with the combat aircraft of other countries without extensive joint training and the use of U.S.-supplied computers and communications equipment; and that "Saudi AWACS operations will depend on U.S. spare parts, maintenance and support of operations."

Fischer also said that "an AWACS aircraft flying close enough to Israel to monitor its aircraft would be vulnerable to being shot down by Israeli fighter aircraft."

Four U.S. Air Force AWACS planes have been stationed in Saudi Arabia since September, when the Carter administration dispatched them to shore up Saudi defenses during the initial phase of the Persian Gulf war between Iran and Iraq. The expectation in Washington and Riyadh is that these planes will remain until the Saudis receive their own aircraft under the planned U.S. package, beginning in April 1985.

The White House official who briefed reporters yesterday, under restrictions that do not permit use of his name, sought to place a major share of the responsibility for the Saudi aircraft sales package on the Carter administration, saying it "had gone a long way toward making this decision."

A senior State Department official, in a separate interview, said a study is under way within the government of crucial details of the military aircraft sale, which is valued at $5 billion, including five AWACs planes at $190 million each.

Among the questions to be addressed in the study, the official said, are a final list of what equipment is to be supplied, what ground radars and other facilities will be tied into the system, where the equipment will be located, and the division of operating responsibility in the decade or longer that will be needed for the Saudis to become proficient in the operation of the highly sophisticated planes.

The State Department official predicted that Israel's concerns will be reduced when the details are decided and made known.