The Reagan administration, in its first five weeks in office, has followed its instincts by rapping the Soviet Union at every opportunity. But it has yet to make a serious start at formulating an overall strategy for the East-west struggle ahead.

Under President Reagan and his dominant policymaker, Secretary of State Alexander M. Haig, Jr., the posture toward the Russians is combative and tough on nearly every question across the broad range of superpower business. Moreover, the heavy emphasis on confrontation, still mostly of the rhetorical and symbolic kind, is not balanced by expressions of desire for U.S.-Soviet cooperation as in other recent administrations.

The Soviet Union, in these early weeks, has returned the verbal fusilades in propaganda forums. However, its highest-level reactions, in the speech yesterday by Soviet President Leonid Brezhev, suggest that Moscow is seeking to portray itself as reasonable and responsible in the face of an unjustified switch in signals from Washington.

Brezhnev's call for a summit meeting, one of the subjects at an expanded session of the White House foreign policy team yesterday, presents Reagan with an attractive option which could be picked up at a later stage. Presidential press secretary James S. Brady said Reagan views the summit suggestion "with interest" and plans to discuss it further in the near future with his own advisers and U.S. allies.

Haig, in a further comment on the Brezhnev speech, said yesterday that the United States is "very interested" in it and that it contains "some new and remarkable innovations." He was not specific about these, but aides expressed belief he was referring, among other things, to Brezhnev's seeming approval of a French plan to extend advance notification of military activities and other "confidence-building measures" all the way to the Urals if the West extends the same limitations in its zones.

Despite Washington's relatively positive response to a relatively Brezhnev speech, there was no discernible eagerness for a quick summit meeting at top levels of the administration. Well-informed officials suggested that much remains to be done before a Reagan-Brezhnev meeting is warranted. And important decisions on strategy, resources and tactics must precede the actions, if they are to be more than random responses to random challenges in a globe that is littered with trouble spots.

At this stage, it is useful to explore and keep in mind what the Reagan administration has decided and done regarding the central question of relations with the Soviet Union, and what has not yet been addressed or completed.

First, it is obvious and much remarked that Reagan and most of his senior foreign policy aides came to office with a deep antipathy for the Soviet Union, and a strong belief that previous administrations did too little, too late, in the face of Soviet expansion. This is the instinct and assessment that undergirds the new administration's hard line on the Russians. a

Second, and less obvious, is the fact that this is a posture toward the Soviets, but far from a global or even bilateral strategy for dealing with them. Although many interdepartmental policy studies have been undertaken on urgent issues in the first five weeks, ranging from El Salvador to Poland to the Persian Gulf, no study has yet been launched to address the central questions of U.S.-Soviet relations across the board.

Some preliminary work is under way under the aegis of the policy planning staff of the State Department. But a full-scale strategic review, which is likely to consume several months, is said to await Reagan's approval of the memoranda from Haig and Secretarys of Defense Caspar W. Weingberger establishing a permanent structure for foreign policy decision-making.

The policymakers of the new administration are well aware that they cannot remake the world at once, and in fact are highly critical of the Carter administration for charging off in all directions to do so without much prior planning and no decision on relative priorities.

At the outset, therefore, the new administration concentrated mostly on those problems and situations in the East-West ledger which were urgent and unavoidable.

It reiterated the Carter administration policy of strongly opposing Soviet intervention in Poland, and warning of the "grave consequences" that such a move would have. In case of a Soviet invasion, according to informed sources, the Reagan administration would demand a general economic boycott of the Soviet Union, and has reason to believe its allies would back this and other dramatic measures.

Because of Poland and East-West tensions generally, the new administration decided against lifting the grain embargo imposed by the Carter administration after the Soviet invasion of Afghanistan, despite Reagan's campaign statements to the contrary. And this week the administration's representatives in Paris will agree to aid the Polish economy by deferring the repayment of more than $80 million in official debt owed to the United States.

No decision has been made on how or when to proceed to renewed negotiations, or even "talks leading to negotiations" between the superpowers on strategic arms limitations (SALT). Brezhnev's surprising willingness yesterday to continue arms negotiations "without delay" despite the non-ratification of SALT II, may increase allied pressures for early action. n

At this point, there is not even a decision on how to manage, or even whether to attend, the next scheduled Soviet-American meeting on arms control, the March 25 meeting of the Geneva-based Standing Consultative Commission which was created in 1972 by SALT I. This is still a matter of controversy within the administration.

By far Reagan's most important East-West initiative, in the sense of an optional decision, is to "draw the line" against communist encroachment at the border of El Salvador, and permit the administration to announce it may "go to the source," identified as Cuba, if outside help for insurgency persists. This willingness to confront and contest was foreshadowed by campaign statements of Reagan and post-election declarations by Haig.

Central America was an obvious choice for the first confrontation, since it is in the back yard of the United States and involves the Soviets mostly indirectly. If it follows its instincts and early ideas, the new administration will confront and contest in other "peripheral" areas of the world, including Africa, the Middle East and Asia. But that will be more complicated and more dangerous, and require a regorous assessment of priorities and repercussions.