The Reagan administration announced yesterday that it will sell Air-to-air missiles and extra fuel tanks to Saudi Arabia to enhance the effectiveness of its U.S-supplied F15 warplanes. The administration cited East-West security considerations and chaged circumstances in overriding Carter administration commitments against such a sale.

At the same time, the Reagan administration promised to supply $600 million in additional arms sales credits to Israel, which strongly opposed the original warplane sale to the Saudis in 1978 and continues to oppose enhancement of the planes' capabilities.

Several Democratic senators quickly announced that they will seek to block the Saudi sale through legislative action. But with a Republican-controlled Senate likley to be sympathetic to the White House position, and the Israeli government signaling a much less active role than in the earlier controversy, it was far from certain that opponents can seriously endanger its chances on Capitol Hill.

The significance of the administration's decisions, both in international and domestic political terms, transcended the importance of the multi-part packages devised for Saudi Arabia and Israel, who have little in common other than their close ties to the United States.

The State Department announcement cast the decisions in stark East-West terms as the consequence of "the serious deterioration in security considerations in the Middle East/Persian Gulf region and the growing threat to our friends there from Soviet and other pressures."

Senior State Department officials depicted the sale as only the first step in a broad new effort to enhance the military capabilities of the United States and its allies in the Middle East.

Other parts of the program, they said, include an increase in the "security supporting assistance" category of foreign aid, said to be among the few items in the non-defense budget permitted to rise, and a speedup in the organization and deployment of the U.S. Rapid Development Force.

"The Soviet invasions of Afghanistan, the turmoil of the Iraian revolution, the Iran-Iraq war and the Soviet presence in South Yemen and Ethiopia underscore the instability in the region and the dangers of Soviet penetration and exploitation," said yesterday's announcement in support of the claim that "circumstances in the region have changed dramatically" since the 1978 Carter commitments.

In a notable shift from the rehtoric of the Carter administration, officials cited a peaceful settlement of the Arab-Israeli conflict as third among the "overriding concerns" of U.S. allies in the Middle East.

The first two "overriding concerns" were listed as these allies' defense against "growing threats to stability" and "our ability and willingness to resist the Soviet advance."

A shift in the emphasis of United States policy from the Arab-Israeli context to the East-West context could facilitate closer cooperation with Arabs and Israelis, with fewer occasions for such head-on political collisions between them as the 1978 Saudi jets controversy. But it is a yet unclear how Middle East nations will regard the much greater emphasis on East-West conflict.

In addition to extra fuel tanks and advanced Sidewinder air-to-air missiles, the Reagan administration announced that it will sell the Saudis "aerial surveillance aircraft," perhaps a version of the highly sophisticated AWACS, and that it "agreed to be responsive" in providing the Saudis an inflight refueling capability such as tanker aircraft.

The Saudi request for special bomb racks for its U.S.-supplied F15s was not approved.

For Israel, the Reagan administration offered an additional $600 million over two years in military sales loans, plus a "much more forthcoming" attitude toward Israel's proposed sales to other countriesa of its homemade KFIR jet fighters, which contain a U.S.-designed engine.

Israeli sources are already suggesting that the terms of the extra loans are insufficient, given that country's severe economic strains. The administration is well aware that Israel's friends in Congress may seek to subsidize the loans or even convert them to grants.

In early congressional reaction, Democratic Sens. Joe Biden (Del.), Alan Cranston (Calif.), and Edward M. Kennedy (Mass.) denounced the Saudi sale and announced an effort to block it by majority vote of House and Senate.

Biden, in a telephone interview, said the he had received no calls of encouragement or discouragement from Israeli officials and that an attitude of Israeli disengagement potentially could reduce the strenght of the congressional opposition to the sale.

The Israeli Embassy, in an official statement, expressed "great concern" about the sale, saying it will "increase the dangers to Israel." The statement added that "an uncontrolled arms race" is no solution to the problems of the Middle East.

The Carter administration, in fighting a tough battle to sell the F15 jets to Saudi Arabia in 1978, promised that it would not supply enhancements such as extra fuel tanks and ground-attack arms.

After the Saudis initiated a new request for such gear early last year and made it a litmus test of their U.S. connection, 68 senators signed a letter opposing the sale. In an 11th-hour bid for Jewish votes, Carter announced last Oct. 24 that there would be "no change" in the earlier assurances about the F15 gear.

In the light of this tangled political history, the continuing requests of the Saudis made the F15 gear the first item of controversial Middle East business for the incoming Reagan adminstration.