The Reagan presidency is a week old and, in the large office in E-Ring, 3rd Floor of the Pentagon, a secretary interrupts Caspar Weinberger with the urgent message that Alexander Haig is calling. From his car phone.

Haig is in one of his high-compression modes.

"You're accusing me of trying to rape the department!" Haig shouts into the phone. Days earlier, the new secretary of state had launched his celebrated Inauguration Day preemptive strike--that memo to the White House in which he sought to redesign all national security decision-making apparatus to make himself preeminent in all areas. Weinberger has just countered with his own White House memo of protective reaction.

A man of lower key, Weinberger listens to Haig's telephonic wrath and demurs that he is making no such accusation. "Don't tell me that," Haig replies. "I have a copy of your memo right here. You're accusing me of trying to rape your department!"

So went the opening exchange in Haig vs. Weinberger, a long-running battle that would blend the best of Lincoln vs. Douglas, Graziano vs. Zale and W.C. Fields vs. Charlie McCarthy. For the record, Weinberger had made no bureaucratic allusions in his memo to rape, but he did incur Haig's ire by making a few uninvited insertions--assorted limits and caveats that he had added to Haig's initial listing of the duties of the secretaries of state and defense. All of the suggested restrictions fell only in the secretary of state's column.

Weinberger has always defined the scope of his office broadly and bristles, those close to him say, at mention of the man who sought to best him in that initial bureaucratic jostling. "Cap is not Machiavellian, not malicious," a senior defense official explained. "I think Cap saw it as a guy trying to push him around. And he thought that he, if anyone, should have been the preeminent guy. Because he's the one who knew Reagan."

In time they would battle over policy and turf, as Weinberger by necessity made up in persistent staying power and longtime California friendships what he lacked in international expertise. He pressed his positions within the Reagan high command with rigidity and determination and wound up having his way on what he felt mattered most.

He won his fight for huge defense spending increases despite objections from many within the Reagan hierarchy. He had his way on such issues as assembling and stockpiling of neutron warheads and his desire for an early vote on sale of sophisticated Airborne Warning and Control System radar planes to Saudi Arabia, despite Haig's strong objections.

Weinberger sees the defense secretary's sphere as a global mix of military and foreign policy. He is perhaps the most traveled defense secretary, surely the most widely traveled in peacetime. He had hoped to be President Reagan's secretary of state; he settled for defense. In his first 14 months in office, he traveled to 26 countries; in a comparable period, his predecessor, Harold Brown, visited 11 countries.

But Weinberger's doctrine has not been nearly as diverse as his itinerary. At virtually every stop, he has preached a steady gospel of anti-Sovietism--more accurately, counter-Sovietism. He established his pattern early.

BRUSSELS--The NATO defense planning committee is in session, and Caspar Weinberger begins his opening statement by passing a small plate of copper circuitry among his ministerial colleagues. His audio-visual prop has been taken from a Soviet submarine detection buoy; its 18 circuit chips, Weinberger says, are made of components identical to those that originate in the West.

"This product is a combination of legitimate sales and espionage," Weinberger says, launching into a warning that will become his frequent NATO refrain about the dangers of doing technological business with the Soviets. Severe economic problems are forcing the Soviets to choose between growth in military or nonmilitary sectors, he says.

He concludes with a statement that will prove to be his guiding principle of policy-making: "This is the perfect time for making life harder for the Soviets instead of easier."

Weinberger came into office with expertise in only one area of international affairs, the Middle East. He acquired strong feelings and inclinations during half a dozen trips to Saudi Arabia during his private enterprise years, known in Washington as the Carter years. He traveled as vice president and general counsel of the giant Bechtel Corp., Saudi Arabia's partner in building refineries and public works.

Today he is sensitive to Saudi concerns and those of other Arab nations and is anxious to mold stronger ties between them and the United States. He credits his experiences in Saudi Arabia for his sensitivity. He worked there with Saudi officials, including Oil Minister Sheik Ahmed Zaki Yamani and, he explains, came to appreciate their perspective.

"When I was at Bechtel, I nearly always went to the ambassador's house and he would have a dinner and I would see some of the people there. But it was just informal. But it did give you an opportunity to learn quite a bit about the country and about the thought and about the way in which they viewed the U.S. I just think we're not in a position to ignore the possibilities of gaining many additional friends in many different parts of the globe."

Weinberger takes care, at every occasion, to emphasize that he does not advocate diminishing U.S. friendship with Israel. Those who know him best at the Pentagon say he strives to maintain this view in private councils, although as one senior defense official noted, this has not always seemed easy. This official said:

" . . . No doubt about it, his views were shaped at Bechtel. When Israel bombed the reactor in Iraq, any chance that Israel had--that was it. He was livid, adamant . . . . He felt we did not have an evenhanded policy in the Mideast. He felt our future in the Mideast should not be tied to Israel.

"He was really turned off by Begin . . . pressuring Reagan on his early visit to Washington . . . . "

Another senior administration official said: "Cap does not see beyond the Begin government to the fundamental questions of Israel. It is Cap's misfortune to deal only with the most undesirable leader, Begin." Noting that Weinberger has no on-the-ground familiarization with Israel, he added:

"Cap and his closest advisers do not have an appreciation of Israel's perilous military situation. Cap is concerned about the Persian Gulf and its security most of all. Cap does not insist on getting enough from the Saudis; he believes it is enough to just keep them functioning."

Weinberger has sought on several occasions to put his Mideast experience to constructive use for Reagan. Having successfully pressed the president to push for an early vote on selling the AWACS planes to Saudi Arabia against Haig's advice, he several times expressed skepticism in National Security Council strategy meetings at State's optimistic assessments of what the Saudis would agree to.

He repeatedly cautioned against a deal with the Senate involving assurances unacceptable to the Saudis. "The Saudi government has always felt that it is very important that they be regarded as a sovereign nation, one with considerable pride," Weinberger said. "And with the sale, you can't put conditions on it that would be unacceptable to the Saudis."

At one point, Weinberger openly expressed doubt when a State Department official assured a White House strategy session that the Saudis "have agreed to" joint AWACS crewing. Weinberger proved correct.

During his recent Mideast trip, Weinberger also sought to promote U.S. military consultation with the Saudis and Arab nations on the Persian Gulf. In a bureaucratically bizarre occurrence, that trip found him touring there while Haig was in the region. Weinberger hoped for a joint statement with the Saudis on formation of a U.S.-Saudi military commission. The Saudis let Weinberger privately read a paper about such a commission but made no comment on it.

Weinberger also sought Saudi assistance in helping the United States establish a relationship of military training and coordination with a little-known group called the Gulf Consultative Council, an organization of Arab gulf nations. Weinberger says the Saudis were quietly receptive. "I think most of the Arab governments are very skittish of any kind of open or visible close relationship with the U.S. for a number of reasons," he says. "And I think we have to understand that and respect it."

On that trip Weinberger also sought to use his Saudi experience to coax Jordan's King Hussein away from his intention to buy mobile air defense missiles from the Soviets. The effort proved calamitous.

The United States has refused to sell Jordan mobile Hawk missiles because of Israeli concern that any mobile, rather than fixed, air defense missiles can be turned against Israel. But Weinberger discussed the possibility of selling Jordan mobile Hawks and F16 jets with Hussein, then told the press about it.

The news reports touched off an explosion in Israel, and Reagan had to assure Israel that no such sale would occur. The controversy was compounded by one particularly inaccurate news report that combined what Weinberger was saying with a distorted comment attributed to a Weinberger aide about how the United States now wanted to "redirect" its Mideast policy, once predominantly pro-Israel.

Since the aide had never said that, the report allowed Weinberger to claim, accurately, that he was the victim of inaccurate journalism. The incident helped to obscure the fact that his natural inclinations on the Mideast have been taking him in a different direction.

One defense official, seeking to explain the problem in Jordan, explained: "Cap sees it as, 'Okay, here's a problem. I ought to try to solve it.' Cap doesn't think of the perception of what he is doing, as Haig does. He doesn't think about, 'What will the Israeli reaction be?' "

Another defense official added: "He and Haig had talked about their mutual concern that Jordan would buy Soviet weaponry . . . . I think he went one step further on his own. I think he felt it was common sense--these people in Jordan are not going to attack Israel. Syria is the enemy, the enemy of Jordan is . . . not Israel."

As Weinberger explains it, however, it becomes clear that he greatly sympathizes with Jordan's desire for mobile missiles and that he does not express compassion for Israel's fear of having such mobile missiles on its border.

Of his talks in Jordan, Weinberger says: " . . . the point was made many times that . . . immobile, fixed anti-aircraft is not a very useful kind of defense and that nobody else has it. And that was therefore understandable that they had to go somewhere else to get it. But that it was unfortunate that they would do anything that would open additional Soviet influence in the region. And they're aware of it. They don't like it. And they nevertheless feel they have to have it."

During the first year of the Reagan presidency, Weinberger enjoyed intramural success in clashes with the vastly more experienced Haig because of:

* His close ties to the president and his Californians. No defense secretary has ever been on such intimate personal terms with the president he served.

* Haig's high-tension performances, which alienated Reagan and his senior advisers.

* The low-profile operating style of then-national security adviser Richard V. Allen, who one day found himself the object of a laughing fit in the Oval Office, as the president and his advisers chortled over a story likening Allen to the monkey who scampers up the tree when the rogue elephants start fighting below.

The arrival of William P. Clark to replace Allen in that basement office in the West Wing of the White House has signaled a new era already being felt in more highly situated chambers, including the offices of E-Ring, 3rd Floor, the seventh floor at the State Department and most of all, in the Oval Office where, paradoxically, all angles converge.

When Weinberger made his first mark here in 1969, he did it in part by quietly bringing in as his temporary assistant a fellow he had known in California, a former chief of staff to the governor who had since moved on to the courts and grown fond of his new title: Judge Clark.

As President Nixon's chairman of the Federal Trade Commission, Weinberger quickly earned accolades, with a reorganization still widely praised. He did it, he says, with Clark's help.

"He really laid the foundation for what some people were kind enough to say was a reasonably successful few months that I had there," Weinberger said. " . . . He was interviewing people, he was giving me recommendations of the present state of the commission, which was unbelievable. He was making recommendations with respect to administrative and internal paper flow . . . . I begged him to resign from the bench and take the top No. 2 position there, and he just felt he could not do that."

Today they talk of mutual admiration. Weinberger: "Clark is absolutely superb . . . . He has all of the skills and none of the . . . personal ambitions." Clark: "We were colleagues in California in 1966. We continue to be ratcheted. We never had a conflict in all those years."

Beyond all that, they are now heading, if not for conflict, at least a reordering of things.

Clark is enforcing a coordination that existed previously only in theory. He was quick to call Weinberger after the secretary's mistimed public advocacy for calling in Poland's debt and carefully spoke not in anger while clearly noting that this was not helpful to the president. When those news stories erupted amid Weinberger's Mideast trip, Clark tracked him with phone calls to his hotel and his airplane to rectify matters quickly.

Clark has been evenhanded. When Haig launched the public relations coup that backfired, dragging a captured Nicaraguan guerrilla into the jungles of the State Department to tell all, Clark pointedly let Haig know that he should not attempt such uncoordinated gambits again. Clark gave no deference to the man under whom he had just served a year as deputy secretary of state.

Clark made no secret of his displeasure with Weinberger and Haig when each scheduled and planned a Mideast trip without consulting the White House or each other until they were locked into their respective itineraries. Clark acted swiftly. He had Reagan issue a directive ordering that plans for all trips be cleared first at the White House.

He enforced the directive promptly by seeing to it that Weinberger's planned trip to Israel next month was canceled. Clark did it delicately but effectively, so that a White House assistant could later say "the decision was roundtabled." That meant, he said, that "Cap agreed it was not the best time to go."

It is significant that Weinberger has responded much differently to Clark's assertion of influence and muscle than he did to Haig's Inauguration Day offensive. Ever the bureacratic realist, Weinberger recognizes that his close ties to Reagan afford no special advantage in this new pairing. Also, he realizes that the system has needed coordination and repair.

So Weinberger and his aides say they welcome insinuation of Clark, even though he brings constraints--and perhaps eventual conflict--to Weinberger's ever-determined reign.

"We now have clear guidance coming out of meetings," one Weinberger assistant said. "What Clark's arrival means to us is a sense of orderliness to the process that did not exist before."

Weinberger is asked what he thinks of the following, contemporary quotation:

"We never articulated our defense strategy in a coherent way. The perception in our country is that we are just sinking our bucks into defense but not an overall strategy."

"No, I don't agree with that," he says. "I can guess who it is."

The quote was drawn from the published notes of Haig's comments at a staff meeting.

"Al Haig's never told me that. He's never indicated to me any problems with that. He's been enormously supportive of our budget and of all of our defense plans. And he has never, in supporting our budget, has never said anything remotely like, remotely resembling that. I don't think he's talking about our defense in that note, maybe somebody else's defense.

" . . . The statement that we . . . don't have a strategy, causes me some problems because we do have . . . a strategy of deterrence. We have a strategy of trying to get enough strength to respond and to be able to respond in a way that will deter the attack in a number of different places around the world at once. And this involves regaining substantial strength as quickly as possible.

"But when people say, for example: you don't have any strategy, you ought to cut your strategy to fit your resources, and then in the next breath they say you don't have enough, and you ought to ask more, I say, 'Well, (a) put in a supplemental, and (b), tell me what it is we should stop doing.

"Should we write off the Mideast? Should we say that we don't have enough resources so we oughta give up all attempts to reinforce the Mideast? Or should we write off Korea? Or should we write off the Caribbean? What is it we should give up? . . . .

" . . . When people say cut your strategy to fit your resources, that sounds great. But it's like so many of these other criticisms: you ever ask for any specifics--just tell me exactly what it is we should do--you don't get an answer."

Epilogue: Across the river, as Weinberger is speaking, Clark has just named another old California friend, Thomas C. Reed, Air Force secretary under President Ford, to do a special study of defense strategy and defense spending for the National Security Council.

Clark has not consulted Weinberger about this. In private discussions with members of Congress and the White House inner circle, Clark has stated a view very similar to what Haig said in private discussions with his staff. Clark feels that defense spending decisions were made without a review of what defense strategy should be.

Preparation of Weinberger's annual defense posture statement was delegated to Undersecretary Fred C. Ikle, and defense officials say Weinberger's major concern about the drafting of the statement was about its timing, not content.

The fact that the National Security Council is undertaking a major and critical review of Weinberger's budget has caused considerable Pentagon concern. The concerns of Weinberger's deputy secretary and alter ego, Frank Carlucci, have been vocal enough to gain attention across the Potomac. "Carlucci is grumbling the loudest," a presidential aide says. "But while they are grumbling, they are also getting in step on it."

Meanwhile, Clark has vowed to become involved permanently and deeply in defense and intelligence budgeting, the task that Weinberger has pursued with determination and inflexibility, with consummate bureaucratic skill and success. Weinberger's short-term success may prove discomforting in the long term.

Defense budgetry is not the traditional fare of presidential advisers on national security. But something about a five-year defense budget that has swelled to $1.6 trillion encourages bending tradition, perhaps with an eye to encouraging eventually bending the rigidity that has characterized Weinberger's Pentagon reign.

After one fractious year, the Reagan White House has come to understand a fundamental tenet of decision-making that applies to both shores of the Potomac.

"We must never lose sight of one basic truth," a senior presidential adviser observed.

"Money is policy."