President Reagan, fighting to save his $8.5 billion aircraft sale to Saudi Arabia from congressional veto, will mount a final lobbying effort tomorrow that White House officials said will continue up to 5 p.m. Wednesday when the Senate is scheduled to vote on the controversial deal.

As the president returned to Washington yesterday from Cancun, Mexico, administration officials said he has invited eight senators to the White House Monday in an effort to reverse the majority now on record as intending to vote for a resolution opposing the sale of Airborne Warning and Control System planes.

The eight are Edward Zorinsky (D-Neb.), William L. Armstrong (R-Colo.), Mark Andrews (R-N.D.), Slade Gorton (R-Wash.), Robert W. Kasten Jr. (R-Wis.), Charles E. Grassley (R-Iowa), Lloyd Bentsen (D-Tex.) and Howard W. Cannon (D-Nev.).

Despite intense administration pressures, 47 of the 50 senators who originally sponsored the resolution of disapproval have given no public sign that they intend to change their stance. Five others also have announced their intention to vote against the sale, making a total of 52 on record as opposed.

If those numbers stand and the Senate follows the lead of the House, which already has voted 301 to 111 against the package, it will mark the first time Congress has exercised its prerogative to veto a major arms sale.

The White House and its allies in the Senate Republican leadership contend that the figures are deceptive and that sufficient votes can be switched in time to give Reagan a majority when the actual vote occurs Wednesday.

The administration's strategy has been to concentrate its campaign of persuasion on freshmen Republicans and Democrats with a reputation for being conservative or unpredictable on national security and foreign policy issues. That approach is evident in the list of senators who have been invited to confer with Reagan Monday.

Of the five Republicans, Armstrong and Grassley are uncommitted, although Grassley has said he is leaning against the sale. Andrews, Gorton and Kasten are sponsors of the disapproval resolution, and all have indicated that they would switch only if the president were able to obtain new concessions from Saudi Arabia giving the United States some form of joint control over the operation of the AWACS planes.

They were among several senators who had called for Reagan to seek such concessions during his meeting in Cancun Friday with Saudi Crown Prince Fahd, but apparently he did not even raise the AWACS issue with Fahd. This is regarded by congressional sources as making it much harder for him to argue to Gorton, Andrews and Kasten that sufficient safeguards already have been built into the deal to prevent misuse of the equipment.

The three Democrats--Bentsen, Cannon and Zorinsky--also are sponsors of the resolution, and they have given no indication that they might change their votes. When the Senate Foreign Relations Committee approved the resolution two weeks ago, Reagan telephoned Zorinsky just before the vote in an attempt to win him over, but the Nebraska Democrat still voted against the sale.

In addition to those who have taken a stance, some of the nine senators still in the undecided column are expected to vote against the sale, and leaders of the opposition have predicted that they could end up with 55 or more votes. In the face of this arithmetic, Reagan and Senate Majority Leader Howard H. Baker Jr. (R-Tenn.) have continued to insist that they will have the votes necessary to protect the sale; but they have refused to identify senators they claim will switch.

The Foreign Relations Committee, in a report made public yesterday, criticized the proposed sale as having "security implications" for Israel and warned that it could escalate the Mideast arms race and draw the Saudis into a future Arab war against Israel.

The report added that some committee members "were deeply perturbed by the repeated assertion that the United States was committed to go ahead with the sale based on U.S.-Saudi discussions which had not been shared with Congress." It also rejected the administration's contention that the sale is a "litmus test" of U.S.-Saudi relations, saying: "It would appear that the relationship of the two nations should not require such tests."