PRESIDENT REAGAN thought to pull the political sting from the Saudi missile sale by pulling the Stinger anti-aircraft missiles from the package Congress rejected two weeks ago. His idea was that a Congress fearful lest terrorists acquire these convenient shoulder-fired weapons would approve the presumably less menacing air-to-air and air-to-ship missiles in the package. This strategy seemed to be working when, late Wednesday, the president vetoed the congressional resolution blocking the sale. The Democratic-led opposition then managed to put off the vote on a veto override until after the Memorial Day recess. It has to be considered a close thing.

Various reasons are cited for Congress' refusal to approve resupply of missiles the Saudis had been permitted to buy before: falling oil prices, the frustrations of Arab-Israeli peace-making, heightened American concern with terrorism, a general tendency to put down Arabs and intimidation by the Jewish political fund-raising groups. These are not so much "reasons," however, as excuses -- inadequate ones -- for an appalling failure of judgment.

Saudi policy has for Americans its disappointing-to-maddening aspect but also its extremely helpful aspect. The balance is greatly in the American favor -- so much so, in fact, that it is a considerable embarrassment to the Saudis, who must constantly justify to militant and radical forces in the area that they are not American lackeys. Their interest in stability and moderation, while it does not solve all of America's problems in the Middle East, makes them at least bearable. You have only to imagine that the country with the world's largest oil reserves was run by Marxists or mullahs to grasp the extra difficulties that might flow as a result to the United States.

The Saudis make their way by subtleties and nuances that tend to flatten out in the open glare of American political debate. It takes some subtlety to appreciate them. But is this really beyond Congress? It is true that the Saudis have their own reasons for a close tie with the United States. But they need to be treated with some respect. To ask their greater cooperation in regional affairs while inflicting upon them the humiliation of public rebuff in a matter -- security -- of the greatest consequence to them is an insupportable inconsistency. It is harmful to the American interest, and it shows the United States is not serious about its foreign policy. This is a veto that must be sustained.