The United States and Saudi Arabia have reached the most serious juncture in their relations since the 1973 Middle East War and oil embargo.

Based on interviews here and in Washington, ties between the two appear to be marked by deepening frustration, conflicting goals and misunderstanding.

Nowhere is this more evident than in the Saudi depiction, and rejection, according to authoritative Saudi sources, of a far-reaching American security offer by Defense Secretary Harold Brown in February.

According to these sources, Washington sought to provide a U.S. military presence in Saudi Arabia in return for a doubling of Saudi oil production, increased support for the dollar and diplomatic backing for the Egyptian Israeli peace agreement.

To a visitor on his fifth trip in three years to this desolate but suddenly blessed country, all this appears symptomatic of a Saudi state buffeted by a period of rough going.

Its two top dynastic and political leaders, King Khalid and Crown Prince Fahd, are in poor health, and the country is suffering the painful side effects of very high velocity economic growth. Regional instablility is adding to an already strong sense of vulnerability, and there is an ebbing of confidence in the power and purpose of its international patron, the United States.

Today, as in 1973, a U.S.-Saudi rift is a matter of grave international as well as bilateral consequence. Saudi Arabia's position as the world's leading oil exporter has become even more crucial than before the Shah's control of Iran's oil riches was replaced by an unstable Islamic republic.

In its unrestrained thirst for oil, the United States since 1973 has increased its foreign dependence so that imports are about half of all U.S. petroleum consumption, while the industrial nations of Europe and Japan have reduced their imports. Well before the fall of the Shah, Saudi Arabia had become the leading foreign supplier to American gasoline pumps and industrial turbines, with export levels to the United States more than double what they were five years before.

There is no suggestion at the official level here that another oil embargo is contemplated in the current level of political discord. Visitors are told, to the contrary, that a breakdown of economic cooperation would be "disastrous to both of us."

Nevertheless, senior Saudi officials make it clear that they consider economic measures to be tools for political objectives.

In support of this view, the Saudi version of Washington-Riyadh relations in the Carter era begins with unilateral and dramatic Saudi action in December, 1976, on the eve of Carter's inauguration, to face down the rest of OPEC at a meeting at Doha.

The Saudi action limiting a price increase, at the cost of a split in OPEC ranks, is described here now as an astute and calculated gesture to a new administration that had not signaled its intentions on Middle East policy.

No such friendly gestures are likely today; and in the present circumstances it requires affirmative Saudi action, rather than just maintenance of the status quo, to allay dangers to the American and other Western economies.

A Saudi decision not to raise oil production beyond the current level-the clear consensus of the Saudi leadership of the time being and possibly for years to come-will perpetuate a tight international petroleum market.

Coupled with the relative decline of Saudi leverage through threats to flood the oil market and the lessening of Saudi determination to hold down prices-both of which are evident at present-the inevitable result will be still higher oil prices and more serious inflationary pressures in the United States and throughout the world.

Hanging over all these questions is the central problem of Saudi foreign policy: the Arab-Israeli dispute.

What is seen in Saudi eyes as an erratic and uncontrollable performance by Egyptian President Anwar Sadat, followed by a Carter administration U-turn from pursuit of a general Middle East peace to an Egyptian-Israeli peace, has produced a split in the Arab world and an agonizing choice for the leaders of this highly conservative government.

The Saudis say they have had to choose between their Arab and Islamic principles, on the one hand, and their U.S. political connections on the other. As confirmed beyond doubt by their breaking relations with Egypt two weeks ago, they have chosen the former.

The choice flies in the face of strong and persistent U.S. efforts at persuasion. Since the Camp David accords in September, Saudi Arabia has received visits (in order of appearance) from Secretary of State Cyrus R. Vance, Assistant Secretary of State for Near Eastern Affairs Harold Saunders, Secretary of the Treasury Michael Blumenthal, Senate Democratic Leader Robert Byrd (acting as a presidential emissary), Commerce Secretary Juanita Kreps, Secretary of Defense Brown and Presidential Assistant Zbigniew Brzezinski. There have also been innumerable top level messages, private and public.

In another dimension, the United States has sought to reassure Saudi Arabia by a special mission of unarmed U.S. Air Force F15 jets, a heavily armed carrier task force on long-term station in nearby waters, the dispatch of U.S. radar reconnaisance the AWACS planes and the emergency supply of nearly $500 million in advanced weapons for North Yemen, a Saudi client on its southern border.

The high point of the U.S. efforts, in the Saudi view, was the proposals brought to Riyadh on Feb. 10 by Defense Secretary Brown. According to Saudi sources, Brown lffered extensive U.S. S-Saudi consultation on all security matters, including "immediate response" counteraction to security threats to joint interests of the two nations, subject to congressional approval.

Brown is said to have offered an increased U.S. military presence on Saudi soil, in effect the establishment of American bases. Joint U.S. Saudi military exercises were also proposed.

The explicitness of the expected return is a matter of interpretation. In the Saudi view, it was clear enough that it return, the United States was asking for an increase in Saudi oil production over time to 16 million barrels a day, roughly double the current output of 8.5 million barrels. In addition, Washington is said to have wanted increased Saudi purchases of U.S. Treasury certificates and other investments to aid the flagging U.S. balance of payments, and support for U.S. Middle East diplomacy flowing out of Camp David and the subsequent Egyptian-Israeli agreements.

The cautious and deliberate Saudis were reportedly startled by the sweeping nature of the American ideas, and distinctly uncomfortable with many of them.

Although they welcome greater U.S. security presence in the area and quietly have accepted a 22-member U.S. military team to consult on defense plans, the Saudis are extremely leary of anything that smacks of a great power military alliance or suggests the status of a military client.

Unlike the Iraqi royal family to the north, which joined the U.S.-sponsored Baghdad Pact in the 1950s and was overthrown in part because of it, the Saudis have had no formal alliances except with fellow Arab states.

Although the bigh airfield at Dhahran in the east coast oilfield area was originally built by the United States as a strategic bomber base, the Saudis wanted no part of such a highly visible American presence in the 1950s and they feel even more strongly now. Moreover, joint exercises and other aspects of an implict or explicit U.S. alliance, in the Saudi view, would risk an embarrassing and unacceptable association with Israel, a close U.S. ally but a Saudi foe.

Mindful of the major battle in Congress a year ago over the sale of F15 warplanes to the desert kingdon, the Saudis reckoned that the promised "immediate response" by the United States might be blocked or long delayed on Capitol Hill if it were ever needed.

The Saudis, in any case, were far from ready to take the oil, financial or diplomatic actions Washington suggested. To cover confusion and embarrassment, no joint communique was issued on the Brown visit.

On the key point of Middle East diplomacy, Americans have been told repeatedly that Saudi Arabia will not and cannot isolate itself from the consensus of the Arab world, and that the United States should not expect the Kingdon to do so.

"Saudia Arabia can't go it alone," said a military officer, adding that this is especially true after the United States showed in Iran now much it will do for its friends.

"We want to cooperate in the economic field, but don't push us in the political field. We can't go down that road with you," said a Saudi with petroleum responsibilities. Similar sentiments were heard from Saudis of many walks of life, including government officials and members of the royal family.

In the U.S. perspective, Saudi Arabia is as much the molder of the Arab consensus as its captive. The Saudi failure to support or even to acquiesce in the Egyptian-Israeli treaty, in this view, saps its chances for success.

A number of senior U.S. officials suggest that the kingdom's leaders have been tempted quietly to support Sadat but have been dissuaded by threats of Arab radicals, especially physical threats to the oil pipelines. Saudi sources do not deny that there have been differences of opinion on matters of policy within the senior circles, but they portray this line of thought as a misreading of the situation.

The Saudis concede that, in the preliminaries to last October's Baghdad summit of Arab states, the Palestine Liberation Organization (PLO) indirectly threatened Saudi oil installations. A top PLO official is reported to have declared that the Palestinian revolution not only protects the rights of Palestinians, but also protects the Islamic holy sites such as Mecca and the oil pipelines.

Saudi Foreign Minister Saud Faisal rejected the threat. According to an account here, he declared that each country has its own means to protect its natural resources. As for the holy places, God would protect them, he said.

There seems no doubt that Saudi Arabia had been pushed along to stronger measures against Sadat than such leaders as Crown Prince Fahd originally anticipated. The reasons probably combine external Arab pressures, the power of internal orthodoxy and the damaging effect of Israeli Prime Minister Menachem Begin's militant statements and actions regarding the West Bank and Jerusalem.

On the eve of last October's Baghdad summit, for example, the Saudis told the United States in a secret message that they would not permit expulsion of Egypt from the Arab League and would work to maintain links with the Egyptian people.

U.S. officials took this to mean the Saudis would and could stop strong anti-Sadat action.

In fact, Egypt has been suspended from the Arab League and other Arab organizations The distinction between suspension and expulsion may be more meaningful to the Saudis than anyone else. Diplomatic ties have been broken, and new military and economic aid to Egypt have been stopped.

The terms of the current Saudi decisions on aid to Egypt, until now murky at best, are reliably reported to be as follows:

Arab League aid of about $500 million per year from Saudi Arabia and other Gulf states stopped the day Sadat signed the treaty with Israel.

Regular Saudi economic grants meeting periodic requests from Egypt, have stopped. These have ranged from $200 million in 1972 to $700 million after food riots in 1977. Saudi military grants for upgrading the Egyptian Army have stopped, except for previously committed transactions such as the $527 million for purchasing U.S. F5 warplanes and $100 million for the purchase of U.S. armored personnel carriers.

What continues at present are economic and financial arrangements with a longer term basis: Joint companies financed by Saudi capital, Saudi underwriting for Egypt to the International Monetary Fund and private and international banks and 2 Saudi concessionary rates for loans to financially pressed Egypt.

Perhaps most important of all, the remittances of the 200,000 or so Egyptian workers in Saudi Arabia have continued to flow back into the Egyptian economy. They may amount to as much as $2 billion per year.

Visitors are told that continuation of the remaining financial backing for Egypt is more difficult every day due to Sadat's increasingly vitriolic attacks. A case in point is his May Day speech last week accusing Saudi leaders of "paying off" lesser Arab states to break relations and saying "we don't care" whether or not the Saudis pay for his American F5s.

In the Saudi view, Sadat's performance since the eve of his journey to Jerusalem late in 1977 consists of private and public assurances of fealty to the Palestinian and inter-Arab cause, followed in each case by compromises to the contrary.

There is less quarrel than one might expect with Sadat's aim to obtain the best deal possible for Egypt, but he is veiwed as headstrong and impulsive in his means and mistaken in his overall strategy.

The Saudis do not seem to believe that Sadat is in much danger of being ousted in the near future, the predictions of the PLO to the contrary. There is a realization here that peace with Israel is highly popular in Egypt because of the economic expectations it has raised. When those soaring hopes are unfulfilled in a year or two, however, as the Saudis believe they will be, Sadat may crash to earth with them.

Sadat is privately given credit here for courage if not for soundness, but the case of Jimmy Carter is the opposite.

Saudi leaders continue to approve Carter's professed objective of a comprehensive peace, but they have concluded that he lacks the will to see it through it a contest with the Israelis. Sadat was right to say that the American held 99 percent of the cards, observed a Saudi source familiar with the thinking of the leadership, but Sadat was wrong to think that the United States would apply enough pressure on Begin to play the cards effectively.

With characteristic subtlety, the Saudis have taken a split-level position on the president starting with the Saunders mission last October. Sources here said Crown Prince Fahd told Saunders at the time, and the Saudis have repeated since, that they accept Carter's word as "sacred." They went on to say, however, that other Arabs are skeptical, and it is up to the United States to convince the Palestinians, Syrians, Jordanians and other actors that Carter means what he says about a comprehensive peace.

In this fashion, the Saudis, in their own minds, have made a distinction between their faith in U.S. sincerity and efforts, and their lack of faith in U.S. results.

Until and unless something is done in the West Bank to demonstrate real movement toward acceptable resolution of the Palestinian problem, in the Saudi view, the chances for regional peace and the state of Saudi-American relations will be precarious. In the American view, the lack of faith and lack of participation by the Saudis and other influential Arabs makes success on the West Bank all the more difficult.

The Saudis expect no results from the Egyptian-Israeli "autonomy talks" about the final status of the West Bank and Gaza Strip. Given the seeming intransigence on both the Israeli and Arab sides, the expectation may prove correct. CAPTION: Map, no caption, By Dick Furno-The Washington Post