Vice President Bush fired off a salvo last week at opponents of the proposed sale of sophisticated radar planes to Saudi Arabia, but it now appears he hit the wrong target.

In a luncheon speech at the National Press Club last Friday, Bush argued that one compelling reason to sell the Airborne Warning and Control System (AWACS) planes was to help the Saudis protect themselves from terrorism instigated by the Libyan leader, Col. Muammar Qaddafi.

Qaddafi, Bush asserted, is "the world's principal terrorist, and trainer of terrorists." Then Bush added: "He's the protector of the likes of Idi Amin."

The charge was true enough. Amin, the former Ugandan dictator who reportedly murdered thousands of people, did take refuge in Libya after he was deposed in 1978.

What Bush and his speechwriters apparently didn't know was that Amin left Libya about two years ago and, at last reports, was alive and well in Saudi Arabia.

Press accounts as recently as two months ago located Amin in the Saudi capital of Jeddah. State Department officials said they weren't sure of his present whereabouts, but conceded yesterday that he owns a house in Jeddah and had been in Saudi Arabia for an extended period at least until a few months ago.

A leading congressional critic of the AWACS sale, Sen. Rudy Boschwitz (R-Minn.), charged yesterday, "It is Saudi Arabia which is the protector of Amin . . . . He has been given hospitality and sanctuary in Saudi Arabia for nearly two years. Nevertheless, officials still attempt to portray Saudi Arabia as a 'moderate' country deserving of our most sophisticated equipment."

By harboring Amin, Boschwitz added, Saudi Arabia may be violating "the spirit of existing law, especially the Arms Control Act, which contains a provision against military sales to countries which give sanctuary to those involved in international terrorism."

There was no immediate comment from Bush, who was traveling yesterday in the Dominican Republic.