Four radar-packed U.S. Air Force airborne early warning planes took off from Tinker Air Force Base in Oklahoma yesterday for Saudi Arabia as part of a U.S. effort to help the Saudis ward off any air attack that might grow out of the war between Iran and Iraq.

The Pentagon said the deployment was based on a request by the Saudi government, which felt the big four-engine patrol planes were needed to beef up its ability to detect low-flying enemy planes that might try to bomb Saudi targets.

While Iran has made no specific threat against Saudi Arabia, the beleaguered regime in Tehran, which seems to be losing the battle with Iraq, has warned other countries in the region and issued general warnings against helping Iraq.

Pentagon officials said yesterday they had no indication that Saudi Arabia was providing military supplies to Iraq, though it is widely held that virtually all Arab nations in the region favor Iraq.

The announcement said the deployment was "purely for defensive purposes" and officials at a background briefing for reporters stressed that the United States wants to "unequivocally reaffirm its position of neutrality" in the conflict.

The deployment, which will involve some 300 Air Force personnel including air crews and ground support technicians, will be temporary. Defense officials said the contingent would be withdrawn "when the crisis eases" but indicated this might not come upon an initial cease-fire because that truce might not hold.

The big planes -- called AWACS, for airborne warning and control system -- are basically flying radar stations and command posts that can scan the horizon out to about 250 miles and spot attacking warplanes trying to slip under beams of ground-based radar. Having four planes in the detachment should allow the Air Force to keep at least one airborne at all times.

As defense officials here explained it, the planes would stay over Saudi airspace, would be manned by U.S. Air Force crews and would remain under U.S. control.

There are no plans to have Saudi personnel on board although officials said not all details of the operation have been worked out.

If unidentified planes are detected heading toward Saudi Arabia, the information would be transmitted to Saudi command posts on the ground. The Saudis would then use their U.S.-built F5 jet fighters or Hawk surface-to-air missiles to try to intercept the invaders.

The plan to send AWACS planes began to take shape last week while the chairman of the Joint Cheifs of Staff, Gen. David Jones, happened to be in Saudi Arabia on a trip that had been scheduled well before the Iran-Iraq fighting began. Sources say the matter arose in connection with Saudi concerns that its main air defenses were traditionally pointed northwest toward Israel and that as a result of its eastern provinces, facing Iraq across the Persian Gulf, were more exposed.

Because the AWACS's electronic eyes can see well beyond Saudi territory and its sensitive antennas can pick up other kinds of intelligence, it is likely the plane would also gather other information on the Iran-Iraq fighting. However, defense officials yesterday insisted that only information relative to Saudi air defense needs would go to the Saudis, and that other information, which the Saudis could possibly pass on to Iraq about the battle, would not be provided.

Officials also indicated there were no plans to provide similar early warning information to other countries by Iran.

One problem, officials said, is that Saudi Arabia surrounds many of the smaller Persian Gulf nations, and it is virtually impossible to tell if incoming planes are headed for one of these nations -- Kuwait, for instance -- or for targets inside Saudi Arabia.

Saudi Arabia is the biggest supplier of oil to the United States and officials acknowledged yesterday that the Saudis normally have a long list of defense-related equipment they are interested in acquiring. At the moment, however, officials say there are no other requests in hand relating to the current battlefield situation. There were some indiciations, though, that possible future Saudi requests would also be aimed at filling gaps in air defense, possibly with better antiaircraft weapons.

U.S. officials said the question of sending the AWCAS planes was discussed intensely with the Saudis the past weekend but that the formal Saudi request came only on Monday. They also said the U.S. jet transports will be landing at Saudi airfields soon to bring in the support equipment and extra personnel for the AWACS operation. The Air Force has about 22 of the AWACS planes in service, with another 14 on order. Four are based in Iceland and the Pacific, spokesmen said.

Pentagon officials said the planes would fly nonstop to Saudi Arabia in 17 or 18 hours, using aerial refueling.

Meanwhile, informants report that informal, working-level discussions have begun between the U.S. Navy and naval officers from France, Britain, Australia, New Zealand and Italy on what kind of a protective force could be set up if it becomes necessary for the West to keep the Persian Gulf sea lanes open. These sources say the talks have not proceeded far enough to produce any agreed-upon plan.

Some states bordering the Gulf, including Saudi Arabia, Oman and the United Arab Emirates, are also being included on the naval talks. Neither Japan nor West Germany would be included in such a multinational fleet, sources said, because of legal restrictions in those countries about operating military forces beyond their local regions.

Military officials do not believe Iran has the capability to mine or otherwise block the vital Strait of Hormuz leading into the Gulf, but said the main threat to shipping, if one develops, would come from an air attack.

British officials said yesterday they were concerned and puzzled by reports that Carter told members of Congress that the United States and allies were preparing to protect the Strait of Hormuz if necessary.

The understanding in London, as in other European capitals, was that this option had been put on ice after Washington did not follow up last week's soundings about expert-level talks on a range of problems posed by the Iran-Iraq conflict, including the flow of oil to the West.

British officials said that "watchful patience" and quiet diplomacy" was the allies' posture. They said, however, that Britain was informed of and does not object to the U.S. decision to send AWACS planes to Saudi Arabia.