The administration, with a big assist from Senate Majority Leader Howard H. Baker Jr. (R-Tenn.), yesterday informed Saudi Arabia that its hope of buying U.S. radar planes depends on Saudi willingness to include American personnel in crews manning the surveillance equipment.

In a series of meetings that shuttled between the White House and Capitol Hill, Saudi representative Prince Bandar bin Sultan was told that such an arrangement offers the only chance of overcoming congressional concerns about retaining some measure of U.S. control over the Airborne Warning and Control System (AWACS) planes.

Informed sources said Bandar was asked whether his government would be willing to give up its longstanding insistence on absolute Saudi control over the five AWACS planes and accept "a technical assistance contract" providing that at least one American be among technicians operating the AWACS surveillance equipment when the planes are airborne.

Whether the idea will prove acceptable to the Saudis was not immediately clear, and the sources said it must be explored further in the next few days through negotiations with the Saudis and with senators who have expressed reservations about the sale.

According to the sources, failure to reach a compromise on the question of "control" seems certain to ensure that Congress will hand President Reagan a stunning foreign policy defeat by blocking his proposed $8.5 billion sale of the AWACS and other advanced aircraft equipment to the Saudis.

There already is an apparent solid majority against the sale in the Democratic House and, as of yesterday, more than half of the Republican Senate was known to be leaning against the deal. A negative vote by both houses within 30 days after the administration formally notifies Congress of its intention would kill the sale.

In hopes of reversing the numbers in the Senate, the administration, it was learned yesterday, secretly asked Baker several days ago to seek a compromise that would allow Reagan, with Saudi approval, to back away from his public stance that no major changes can be made in the sales package.

Baker's task was to find a means of reassuring skeptical senators that the AWACS will not be used in ways that would jeopardize the security of Israel, which Saudi Arabia regards as its enemy, and that the equipment's highly secret radar and computers will be protected from falling into the hands of U.S. foes.

After some secret contacts with various of the parties involved, Baker met with Reagan at the White House early yesterday and then went to the Capitol where he began detailed discussions with Bandar, son of the Saudi defense minister, Prince Sultan.

Also at the meeting in Baker's office were Reagan's national security affairs adviser, Richard V. Allen, and Sen. John G. Tower (R-Tex.), chairman of the Armed Services Committee and a strong backer of the sale.

At midday, Baker and Bandar returned to the White House, where the president is understood to have told the prince that he believes the sale is in the interests of both countries and to have made a plea for flexibility by the Saudis.

In the afternoon, Baker met at the Capitol with Israeli Ambassador Ephraim Evron to discuss what safeguards might induce Israel to drop or moderate opposition to the sale.

Apparently, the afternoon's key event was a long meeting in the office of Sen. John Glenn (D-Ohio), the Senate's most vocal proponent of the United States retaining joint control of the AWACS.

Glenn has said he will not vote for the sale in its current form. If a compromise acceptable to him can be reached, his support would have great influence on many other senators who have endorsed his call for joint control.

Attending part of the meeting in Glenn's office were Bandar, Baker, Allen, Tower and Sen. Paul Laxalt (R-Nev.), Reagan's closest friend in the Senate.

Despite this intense round-robin of meetings, sources familiar with the talks stressed that, as of last night, it was not clear whether they would lead to anything concrete and that several more days are needed to ascertain whether the administration and Senate can pull away from their collision course over the AWACS controversy.