The Reagan administration, in relinquishing to Great Britain $3 billion in jet fighter sales to Saudi Arabia, loosened the U.S. grip on a lucrative military aircraft market while complicating Israel's security needs, defense industry analysts said yesterday.

Saudi Arabia had sought to buy 40 F15 fighters from the United States but turned to Britain for its Tornado combat jets after the White House delayed approval of the F15s for fear of upsetting Israel's supporters in Congress.

An official of McDonnell Douglas Corp., which manufactures the F15, said that, though the Saudi-British agreement represents a significant loss for the company, it hopes to make subsequent sales to the Saudis and gain contracts to upgrade the 62 F15s sold to Riyadh in 1978 after a fractious congressional debate.

But several industry analysts said the sale is likely to lock in British suppliers, excluding McDonnell Douglas in the long run. Once the Saudis establish supply lines and train pilots for the Tornado, they may find it easier to deal with London for additional purchases, the analysts said.

"It calls into question the kind of market share we will have in Saudi Arabia for the future," said Michael Gardner, an analyst for Shearson Lehman Brothers. He added that, because of sagging international oil prices, this may be Saudi Arabia's last large aircraft purchase for several years.

Other analysts said that, in passing up the F15 sale for reasons of Israeli security, the administration may have wrought even greater problems for the Jewish state.

U.S. officials said the White House reportedly balked at Saudi plans to station F15s near Tabuk, about 100 miles from Israel's Red Sea port of Eilat. But, in acquiescing to the British sale, the administration gave up leverage on where and how the aircraft can be deployed, according to a former defense official familiar with the issue.

"The British impose fewer controls when they sell an airplane than we do," the official said.

Israel may also feel more threatened by the Saudi purchase of 48 Tornado, a sophisticated aircraft capable of penetrating hostile territory at low altitude and dropping bombs within 100 feet of a designated target, said Wolfgang Demisch, an analyst for First Boston Corp.

Demisch called the Tornado an "overwhelmingly offensive" weapon compared with the F15 interceptor, whose primary role is to shoot down enemy aircraft.

"I can't identify any winners outside the British aerospace industry," he said. "The Saudis have a headache in setting up a bureaucracy to handle the British bureaucracy.

"For the United States, it's a hit on its balance of payments and means a major loss of market share and influence in a part of the world that is pretty damn important to us. Our relations and insight with the Saudi military are going to be negatively impacted.

"From the perspective of Israel, it's not thrilling to have a full-fledged strike aircraft on its borders," he said.

Demisch said the administration's reported rationale on shelving the Saudi deal in an effort to ease congressional passage of military aircraft sales to Jordan and Egypt reflects a lack of coherence in U.S. foreign military sales to friendly nations.

Other defense analysts expressed less alarm about the planned Saudi purchase, which includes at least 20 British-made Hawk trainer-fighters.

Despite the inroad in the virtual U.S. monopoly on sale of military aircraft to the Saudis since the 1960s, they said they view the Tornado deal as a one-time arrangement that does not preclude future McDonnell Douglas sales of F15s to the Saudis.

"Given a different political climate and a more courageous administration, I think the Saudis might buy more F15s later on," said David Smith, a defense analyst for Sanford C. Bernstein Corp. "It's purely political."

Another defense expert said the next time the Saudis want fighter jets, "it could be a whole new ball game. This thing can reverse itself very quickly."

A McDonnell Douglas official said his firm expects to continue sales of other weapons to Saudi Arabia, including Harpoon and Dragon missiles and data-processing equipment. Moreover, as the F15 is upgraded, he said, the Saudis may want to add the improvements.

He noted that supply lines of U.S. military equipment normally outlast European models because American firms have the industrial base to upgrade products. Nevertheless, the official said, "right now, the door seems closed" for additional sales of F15s to Saudi Arabia.