President Reagan, fighting to save his embattled proposal to sell radar planes to Saudi Arabia, tentatively plans to send a high-level delegation including members of the Senate to the Persian Gulf kingdom in an effort to win Saudi approval for joint U.S. operational control of the aircraft.

Informed sources said last night that the idea of the trip is being discussed in direct contacts between Washington and Saudi leaders, and that the Saudis have not yet agreed to it.

The sources said the membership of the proposed delegation is undecided, but they emphasized that it almost certainly will include Sen. John Glenn (D-Ohio), the Senate's leading advocate of retaining joint control over the Airborne Warning and Control System (AWACS) planes.

Several senators have associated themselves with Glenn's position that such control is necessary to ensure that the planes are not used against Israel, which Saudi Arabia considers its enemy, and that they are properly protected from falling into the hands of U.S. foes.

The proposed $8.5 billion sale of AWACS and other aircraft equipment can be blocked by a vote of both houses of Congress. Since there is an apparently solid majority against the deal in the House, the administration has pinned its hopes on the Senate, where a majority is leaning against the sale.

Administration officials see Glenn as potentially pivotal in reversing the Senate situation, and their proposed compromise was crafted, in part, to woo his support. He discussed the idea in detail Thursday with the Saudi representative here, Prince Bandar bin Sultan, and again with senior administration officials at a two-hour White House meeting yesterday.

Adding a note of urgency to the administration's need to convince Glenn that the compromise will ensure sufficient U.S. control was the revelation yesterday that part of the revised package would involve equipping the AWACS with advanced electronic equipment not included in the original deal.

Precisely what this additional equipment would be was not immediately clear. But congressional sources said the administration appears to be talking about highly secret communications links that would allow the planes to contact ground stations and relay intelligence without fear of jamming.

That raised questions from several senators about whether the compromise would give the Saudis too much in exchange for what some contended is a "cosmetic change" that would not give the United States any real control over use of the planes and intelligence data they collect.

Among those making this argument in emphatic terms was Sen. Henry M. Jackson (D-Wash.), one of the leading opponents of the sale. "The administration is going to come up with what looks like American command and control, but when you look at the fine print, it's going to be Saudi control," he said.

In Jackson's opinion, "That won't fly in the Senate." He predicted that the only kind of compromise capable of turning around the Senate majority now leaning against the sale would be agreement for a joint U.S.-Saudi command similar to the system used by the United States and its North Atlantic Treaty Organization partners to operate AWACS in Europe.

Despite Jackson's prediction, the administration's new proposals seem to have pushed many senators, including some who had been outspoken opponents, into reserving judgment until they know more details of the compromise plan and whether it is acceptable to the Saudis.

That is why Glenn has become so important to administration strategy. Following his White House talks yesterday, he said only that "we are still considering all aspects of the situation" and refused to elaborate on where the discussions stood.

Reliable sources said, though, that Glenn regards the current administration plan as falling considerably short of his call for a joint command.

The senator's attitude will take on even greater significance if the administration adds the electronic gear to the AWACS package. With the added equipment, the Saudis would, in the theoretical event of a war, be better able to control from the ground the movement of fighter planes.