Defense and intelligence data are the gist of national security and state secrets in most world power centers. In Saudi Arabia, it is different.

For the Saudis, the location and amount of the tens of billions of dollars they own are as closely held as the Pentagon's information on the location of Polaris submarines in America's nuclear strike force. Saudi holdings in the United States are so sensitive that the U.S. Treasury cooperates with Saudi Arabia in keeping Americans in the dark on this subject.

That highly secret figure is now between $35 and $40 billion, according to informed sources who have dealth with this question for several years.For much of this year, Saudi Arabia had been purchasing more U.S. Treasury bonds than the traditional big buyers like West German. Saudi purchases easily outstrip those of any large American corporation or bank.

These enormous petrodollar holdings, ammassed in this decade alone, have transformed the oil-producing desert land of less than 5 million into a major player in World monetary and financial circles.

In all, Saudi foreign holdings exceed $60 billion. They represent what Foreign Minister Saudibin Faisal and other officcials call a potential "money weapon." The funds and investments could be used at will to undermine the economy of the industrialized world.

Such moves, however, would also destroy the developing Saudi economy. Moreover, they would be totally out of character for the Saudis, who survived in the decades before oil survived in the decades before oil wealth began pouring in employing by a willy brand of statecraft that can be traced back to the Hair of Mu'awihyah.

Mu'awihyah, the first Omayyad caliph in the seventh century, fashioned a policy that the explained this way: "If so much as a hair ties me to an ally, I will do everything I can to make sure it does not break. I [TEXT OMITTED FROM SOURCES] pulls, I will loosen. If he loosens, I pull."

For Saudi Arabia today, Mu'awiayah's hair is the checkbook. By skillful use of dollar diplomacy, the Saudis have attracted and neutralized past Arab enemies. Egypt, Syria and the Palestinians may slash at each other as the wheel of Arab politics turns; none of them, however, can afford to break the financial threads that the Saudis hold so lightly.

Close to home, Saudi checkbook diplomacy is an intricate network of influence made up of billions of dollars in straight grants, arms purchases, charity, economic aid and in some instances "insurance" payments that [TEXT OMITTED FROM SOURCES] out of the desert kingdom.

In the West, the Saudis and placing their wealth in a manner calculated to tie them more tightly to nations that can protect them militarily, provide markets for their oil and petrochemical exports, and ship the materials and technology they need to develop their wastelands and scattered desert tribal villages. In practice this means the United States.

But increasingly it appears that these trade and finance links possess an extra dimension that makes them the strategic near-equivalent of the petroleum extracted from American managed fields in Saudi Arabia and shipped, in growing quantities, to the United States.

Washington has evidently prevailed upon the Saudis to make financial choices that are highly favorable to the United States but optional for them. The tradeoff appears to lie in the basket of military training, implied security commitments and political help that the United States provides the Saudi ruling family.

Neither side appears to want close public scrutiny of that tradeoff. At the Saudis' request, the Treasury refuses to make public the amount of Treasury securities or direct investments the Saudis hold. The monthly Treasury Bulletin publishes detailed country-by-country information for many nations, but it does not list those facts for Saudi Arabia.

Saudi Arabia's refusal to have it money in the United States publicly counted stems partly from traditional reticence in such matters. But is also represents a pragmatic assessment by the Saudis, who fear that publication of the figure will give poor Africans and Arabs more ammunition for arguments that the Saudis are not dispersing enough of their surplus cash to the world's needy.

The Saudis are buying up to one billion dollars worth of Treasury notes, bills and bonds every three months. The quarterly purchase varies according to the amount of financial "paper" the United States puts on the market but, in all, the Saudis are reported to have amassed $25 to $30 billion in Treasury an other government securities, such as Federal Home Loan Bank Board issues, in five years.

These purchase give Saudi Arabia significant leverage in American credit markets. The effect of the purchases thur far - evidently intended by Treasury - has been to keep U.S. commercial credit rates stable and slightly lower. The Saudi share of government issues free other investment capital for non-federal and corporate borrowers. The Saudis are also chaneling huge amounts through the commercial loan banks such as Chase Manhattan, First National City and others, who alse shift massive amounts of Eurodollars held by the Saudis.

For American economic planners, this adds up to a much more comforting picture than they might have expected in 1973 and 1974, when scare headlines predicted an invasion of American industry and finance by "camel money." That invasion has not happened, in part because "we have confined our foreign currency holdings to investments in financial assets," Abdul Aziz al Quraishi said pointedly, but "for a variety of reasons, other means are not open to us or else present political or financial problems as bad or worse than the inflationary problem."

Even with the purchases of American securities, the Saudis have enormous amounts left over for use at home and abroad. Unable to spend much of its $35 billion annual oil income ($5 billion of which comes out of American pockets), the Saudis have ammassed an officially stated reserve total of $27 billion, second only to West Germany.

More importantly, the Saudi accumulation of foreign holdings since 1970, when the kingdom actually ran a trade deficit, is larger than any other country in the world. For every surplus dollar West Germany stored away for a rainy day in the past seven years, the Saudis were adding three, than $100 billion in reserves at its present rate of accumulation.

Saudi Arabian cash exports to the Third World are also intended to strengthen the kingdom's stragetic bond with the United States as well as strengthening its position more generally. Saudi foreign economic policy aims at bolstering governments that line up with the shared U.S.-Saudi goal of limiting Russian and Communist influence.

A second goal, of propagating Islam and aiding poor Moslem countries, normarlly presents no policy conflict with Riyadh.

Quraishi and other Saudi officials report that the kingdom has granted $14 billion in aid and soft loans over the years to poor contries, a rate that the Saudis say is 16 times higher than the proportionate national total given by most developed countries. In 1975, Saudi Arabia doled out $5.7 billion in foreign aid, according to the Saudi Finance Ministry. The U.S. figure for that year was $4.9 billion.

The largesse had focused the attention of money-short statesmen throughout the world. During a 45-day period last year, 21 heads of state - some without invitation - braced themselves for the 120-degree heat of Saudi summer and went in search of assurances about money and oil.

More went away with less than they wanted than the Saudi aid figures would suggest. In their few short years of dealing with much of the world as a potential Uncle Saudi - a 1970s version of the chewing gum and money-bags dispensing America of post-World War II - the Saudis have quickly come to establish priorities for their largesse.

According to clossified intelligence estimates, about 50 countries get a piece of the $10 to $12 billion a year the Saudis put into economic aid and arms buying for others. The clients' ranking says much about what the Saudis are trying to achieve or, as their critics would suggest, what they are trying to buy.

The first circle circumscribes the Arab world, centering on countries that have in the past threatened the kingdom. Instability in NOrth Yemen brought a crippling war-by-proxy with Gamal Abdel Nasser's Egypt a decade ago, so special attention is paid today to the Yemens and to Egypt, countries that have been recent targets for Soviet pentration.

"One of our objectives" in granting aid to others countries "is to remove our area from international competition," the Saudi Foreign Minister, Prince Saud, said in an interview.

Egypt now receives more than $2 billion a year in economic aid, and Riyadh adds up to $1 billion more for Cairo to buy arms from France, Britain and, if they will sell to Egypt, the Soviet Union and its allies. The Saudi financial safety net has enabled Anwar Sadat to break Egypt's military allience with the Russians, launch the 1973 war against Israel and now undertake his daring attempt to secure a peace treaty with Israel.

In all, Egypt, Syria and Jordan get about 40 per cent of a year's total Saudi aid. Mainline groups in the Palestine Liberation Organization get about $10 million annually in direct payments, intended to encourage moderation in the guerrilla organization and in part to make sure the Palestinians do not mount anti-Saudi operations.

The Saudis are also using their funds to bolster friendly regimes along the Red Sea, especially in the Sudan and Somalia. They provide several million dollars in cash and arms to the Eritrean Liberation Front, which flirts with Marxism but has the fortune to have as its foe the Ethiopian government, which enjoys the usual backing of all three of Saudi Arabia's main enemies in life - the Soviet Union, Israel and Libya's Col. Muammar Quaddafi.

The Red Sea countries and movements draw the biggest share of the $4 billion that Saudi Arabia allots annually to Moslem states in Africa and the Middle East. That leaves about 5 per cent of the total aid for a small group of Third World countries selected because they oppose communism - Taiwan and South Korea being clear examples - or for a rare payment to bolster Saudi Arabia's Third world credentials, such as a $5 million outlay to Rhode siare black nationalists.

In sum, the Saudis are spending billions of dollars in an arc of influence that extends from Morocco eastward across Africa and the Middle East and deep into Asia. It is an arc that, by design or by accident, could easily have been traced by an American administration eager to help new difficulties in persuading Congress to appropriate money for such causes.

Within that arc may also lie eventual problems for the Saudi-U.S. special relationship, which ramains largely untested. The Saudis, for instance, have recently promised to buy $500 million in weapons, for pakistan, in part to replace Americans fighter bombers the Carter administration is refusing to send Pakistan in a dispute over nuclear proliferation. Saudi aid in this case will effectively permit a former U.S. client to circumvent the Carter administration's widely advertising commitment to reducing arms transfers and dangerous nuclear technology.

"Saudi power may seen like a good temporary substitute for American power in some parts of the world," says an American official with experience in the Middle East. "But we cannot let it proliferate unexamined. Saudi Arabia is not Maine or Hawaii. They know that, even if they often act as if they were. And we have to remember it too."