Potential differences about how to deal with the new Soviet leadership will not hit many headlines during United States Secretary of State George Shultz's visit to Bonn Dec. 7-8.
But they will be the most important topic discussed.
The differences are still only potential. And they are echoed in still unresolved differences within the Reagan administration itself. The warning signals, however, are already visible.
The incipient divergence revolves around two basic questions:
* How close to collapse is the Soviet empire and its economy?
* Should the West in fact compromise on intermediate-range nuclear arms control if the Soviet Union shows some sign of compromise?
For now, allied strains over Soviet policy have been muted. Neither the American nor the West German nor any other major Western government thinks that the uncertain early months of a Kremlin succession are the right time to launch a major initiative in East-West relations. And all are united in regarding Moscow as a military threat if it is not confronted with a military balance.
Over the longer term, however, a fundamental decision will have to be made about the appropriate combination of Western carrot and stick to offer the Brezhnev succession. And this will follow largely from the prevailing image of the Soviet Union.
If the Soviet Union is a dangerous military giant but is facing internal economic and imperial crises, then the proper Western policy is unremitting toughness. This is the view of the outgoing Soviet specialist on Reagan's National Security Council, Richard Pipes, and of some key officials in the Pentagon.
This view underlay Reagan's imposition of economic sanctions last June on Western European firms that exported equipment to the Soviet Union for the new Siberian gas pipeline. It underlies as well the argument that the US can win the arms race by outspending the Soviet Union until the Soviet economy collapses.
If, on the contrary, Soviet economic and nationalities problems can be contained by a combination of muddling through, low popular expectations, and an effective internal control apparatus, then unremitting Western toughness would backfire. Far from forcing the Soviet Union to its knees, it would only help to unite the Soviet elite and even the man in the street in chauvinistic opposition to foreign pressures.
Moreover, if the Kremlin leaders are rational beings who place priority on preserving what the Soviet Union has achieved in its 65 years, then it behooves the West to offer Moscow economic incentives for good behavior as well as disincentives for any military adventures.
This tends to be the view of Europeans across the entire political spectrum, ranging from Bonn's and London's conservative governments to Paris's socialist one - and of the US State Department as well.
This view underlay the unanimous European defiance of Reagan's prohibition against Western European export of licensed American gas pipeline technology to the Soviet Union - and European worry that the sanctions meant an American turn to vain economic warfare against the Soviet Union. It underlay, too, European relief when Reagan finally lifted the sanctions in November.
There are some indications that the White House and Pentagon may not accept this view of the State Department and the NATO allies. Hints have surfaced already in for example November's German-American conference in Bonn sponsored by the conservative-linked Konrad Adenauer Foundation.
In one sense the conference was a conservative love-in of the sort that Reagan Republicans and then out-of-power West German Christian Democrats have reveled in for the past two years. Participants on both sides included some authentic cold warriors. But the top spokesmen for Bonn's new conservative government - including Defense Minister Manfred Worner and Alois Mertes, Foreign Ministry parliamentary state secretary - were deliberately moderate in their approach.
Dr. Mertes, for example, called for ''understanding'' (though not ''acceptance'') of the Soviet security paranoia, and he emphatically rejected the view that the Soviet Union is facing imminent domestic collapse. Some American participants serving in or closely connected with the Reagan administration contested him on both counts.
This dichotomy will have to be resolved before the West can unite in the immediate task of writing 1980s guidelines for East-West economic intercourse. This was the tradeoff (according to the Americans, though not according to the French) for the American lifting of the sanctions.
The second major issue of intermediate-range nuclear arms control will presumably have to be resolved by next spring or summer. At that time - shortly before the start of scheduled deployment of new NATO missiles if there is no arms control agreement - it is widely expected that Moscow will offer some new concession. At that point European governments will be under enormous public pressure to treat the Soviet offer seriously and display a Western willingness to compromise. The grave penalty for not doing so - especially in West Germany - could be the loss of public support for nuclear defense altogether.
Compromise on intermediate-range nuclear arms control goes against Pentagon instincts, however. At the winter meeting of NATO defense ministers in Brussels in early December, Defense Secretary Caspar W. Weinberger impatiently shot down the trial balloon of compromise lofted by British Defense Minister John Nott and even NATO Secretary-General Josef Luns.
Both of the latter had alluded to possible movement away from the American-tabled ''zero option'' of no new NATO missiles in Western Europe in return for dismantling of already deployed Soviet intermediate-range missiles. They did not specify what this might entail, but the possibilities usually discussed include a merging of the intermediate-range with the strategic US-Soviet arms control negotiations; some limited inclusion of French and British nuclear capability in the European balance; and a restriction of the geographical arms control zone to Europe (rather than the global limits sought by the US).
In a press conference Weinberger dismissed any notion of modifying the zero option. Instead, he asserted - rather in contrast to Washington's previous conspicuous consultation with its allies on the Geneva talks - that the negotiating position is America's alone to decide.