Having decided not to fight a futile battle against the sale of sophisticated U.S. aircraft equipment to Saudi Arabia, Israel is focusing on what it considers a broader -- and more ominous -- threat of a Middle East arms race in which the Saudis' advanced weapons could fall into the hands of radical Arab states.

Leaders of the government of Prime Minister Menachem Begin have resigned themselves to the U.S. sale of fuel pods, advanced missiles and other equipment that will boost the operational range of 60 F15 jets that Saudi Arabia has already ordered. Some Israeli officials are convinced the Saudis also will eventually get four Advanced Warning and Command Systems [AWACS] aircraft that they have requested in the face of intense Israeli opposition.

But the Israelis have far from given up their resolve to hold the Reagan administration to what they regard as an American obligation to protect the existence of the Jewish state by assuring Israel's qualitative advantage in the arms balance in the Middle East.

Besides the Saudi F15s, Israeli officials cite as concerns the $160 million sale of 100 M60A3 tanks to Jordan last year, with an option to purchase another 100 later, and another U.S. deal with Amman, sent up for congressional approval March 4, for 24 TOW missile-equipped AH1S Cobra helicopters at $156 million.

With increasing urgency, Israeli leaders have been warning that the United States is falling into the same trap in which it became entangled in prerevoluntionary Iran by pouring sophisticated weapons into countries with inherently unstable governments without regard of where or how they may be used in the future.

While continuing to utilize the threat of a direct Saudi strike as an argument, Israeli leaders have widened the thrust of the case considerably, examining the arms supplies against what they regard as the broader realities of Middle East instability and the prospects of longevity of the Saudi monarchy.

In a recent white paper entitled "Selling Boomerangs to Saudi Arabia," the Israeli military command argued:

"It seems almost tautological to state that one of the most important lessons which the United States may derive from the Iranian crisis is that it should be more selective in the types of governments which it chooses to support. In recent decades, the United States has made a policy of backing strongman regimes or monarchies lacking in popular support, on the sole ground that their orientation is pro-Western."

The paper went on to warn that in Saudi Arabia as elsewhere the outcome could be: "U.S. support for a corrupt government or ruler, granting of large-scale materiel and military aid, an eventual coup or revolution . . . the employment of the confiscated materiel against the United States or the West."

Warning that the menaces that confront Saudi Arabia are internal, and not external, the defense position paper says that in the trauma of political upheaval, the Saudis' U.S. arms stockpile could fall into the hands of revolutionaries, neighboring radical states such as Iraq or even the Soviet Union. The paper cited recent reports that Saudi Arabia has already transferred 200 U.S.-made artillery pieces and an unspeciied number of French-built Amx30 tanks to Iraq.

An intelligence analyst in the Israeli Foreign Ministry said such arms turnovers would be accelerated in the event Saudi Arabia was attacked from the outside. The only conceivable outside military threat to the Saudis, he said, would come from a Soviet-backed invasion by Yemen, but that if this were to happen Saudi Arbia could be forced to turn to Iraq, into whose hands sophisticated weapons would fall.

Responding to suggestions that the United States could balance the supply of advanced weapons to Saudi Arabia by selling similar systems to Israel under special terms, Israeli Foreign Minister Itzhak Shamir told the parliament:

"To our regret, we must state that we do not see this as a solution, or as a way out.

"The state of Israel will not be able -- even from the economic point of view -- to withstand such an arms race, and it is our duty to call upon the government of the United States and all the other countries of the world to put a halt to this unrestrained flood of the tools of destruction which will, sooner or later, cause a dangerous explosion."

In an attempt to balance the Saudi deal, the United States is reported ready to provide Israel with $600 million in preferential financing to purchase 10 more F15s. Israel had earlier ordered 40 of the jets and a number of them already in service

The Reagan administraiton also has said it will be more lenient on authorizing sales of Israeli-built Kfir jet fighters with U.S.-licensed components and to give Israel enhance early warning capability.

Sources in Israel's defense establishment, expanding on Shamir's economic theme, say that since Israel has already reached a saturation point in military spending -- 40 percent of the country's budget goes to defense -- it could be forced to place greater emphasis on preemptive strikes in its defense strategy.

The preemptive strike, as exercised in the 1967 war with crippling effects on Egypt's and Jordan's air forces, has always been an important part of Israel's strategic concept. But military analysts say that it is likely to become more central to defense planning if the Israeli Air Force loses its qualitative advantage in the Middle East.

Israeli arguments against U.S. sale of advanced weapons to Saudi Arabia had undergone a metamorphosis since the days when pro-Israeli forces in Washington unsuccessfully tried to defeat a bill approving the sale of 60 F15s to the Saudi kingdom in May 1978.

Then, the relatively simple thrust of the Israeli argument as that Israel, with 65 percent of its population and 75 percent of its industry concentrated in the narrow costal plain around Tel Aviv, would be highly vulnerable to a devastating attack by aircraft as advanced as the F15. The Israelis raised doubts whether the F15 would really be useful solely for defensive purposes, as Saudi Arabia claimed, and warned of the increased threat from a country that had assisted in four Arab wars with the Jewish state.

In reply, the Carter administration argued that Saudi Arabia needed the ability to protect its oil wealth and territorial integrity from air attack, and that, anyway, the F15s would not have fuel pods and bomb racks that would give them offensive capabilty.

Israel now says the fuel pods to be sold to the Saudis will increase the F15s' range by 90 percent, allowing them to reach Israel from anywhere in Saudi Arabia.

But when it came time to unleash a major lobbying effort against sale of the extra F15 equipment, the Begin government uncharacteristically decided not to engage the Reagan administration in Congress. Foreign Ministry sources explain the reticence by saying they find no point in undermining the Israeli lobby's effectiveness in Washington by backing an already lost cause and that Begin wanted to demonstrate Israel's trust in the new U.S. administration and strengthen Israel's ties with Reagan at the outset of his presidency.

In a March 9 Cabinet meeting, there reportedly was an implicit understanding among ministers that while Israel would not forcefully oppose the sale in Congress, Israeli leaders would continue to speak out about the danger of the increased range for the Saudi F15s.

Linking the range with what it sees as recent signs of Saudi bellicosity, Israel is portraying itself as more vulnerable to attack from the east than ever before. Its leaders particularly bridle at explanations from Washington that Saudi Arabia is embarked on a course of pro-Western moderation.

"Saudi Arabia does not deserve the title of 'moderate,'" said Shamir. "This state has participated in all the wars against Israel. It orchestrated the conference which declared jihad [holy war] against us. It is the major financer of Palestine Liberation Organization terrorism. It worked persistently and agressively against the peace process."