West Germany is putting pressure on the United States to protect European interests in strategic arms negotiations with the Soviet Union and thus bringing to a head what officials here, in Paris and Washington, and at NATO headquarters in Brussels view as the most sensitive issue now confronting the North Atlantic Alliance.

The issue involves trying to establish a rough balance of nuclear and conventional military power in Central Europe - between the Soviets and Western Europe - once Moscow and Washington have hammered out a new SALT agreement that roughly equalizes the missile and bomber forces that could attack each other's homeland.

The West Europeans - especially the West Germans - are increasingly expressing concern that unless something is also done about the growing Soviet medium-range missile and bomber forces aimed at Western Europe rather than at the United States, the imbalance could eventually erode West European confidence and lead to unforseen shifts in political and military attitudes in Western Europe and possible in the Soviet Union.

In an important but little-noticed speech to Social Democratic Party policymakers here three weeks ago, Bonn's defense minister Hans Apel, said solving the problem of these so-called "gray zone medium-range weapons is one of the most important security tasks confronting the NATO Alliance today."

West German Chancellor Helmut Schmidt is expected to address the issue publicly next week during a German-Atlantic Society meeting in Hamburg.

A solution could involve building new medium-range weapons to offset the Soviet arms or opening up the U.S.-Soviet strategic weapons negotiations to a vast array of tactical allied jets and missiles based in Europe that the United States has managed to keep off the bargaining table for the past 10 years, despite Soviet complaints.

The issue is technical, complicated and permeated with fears that are never quite stated publicly. For these reasons, it has attracted relatively little public discussion. But, as one top West German official said, there will be heavy emphasis on this and it will become . . . more politically sensitive.

European concern surfaced for the first time publicly almost a year ago, in a speech by West German Chancellor Helmut Schmidt to the prestigious International Institute of Strategic Studies in London. The speech attracted little press attention, in part because it was delivered in London at a time when the German and Western press were preoccupied with terrorist actions.

But the speech set off alarm bells in some top levels of the State Department.

In it, Schmidt pointed out that a SALT agreement between the United States and the Soviet Union not only "codifies" the strategic arms balance between the superpowers, but also "neutralizes the strategic capabilities" of both.

"In Europe, this magnifies the significance of the disparities between East and West regarding tactical nuclear and conventional weapons," Schmidt said. We Europeans must be anxious to insure that these negotiations do not neglect those factors which make up NATO's defense strategy." The last Comment was a reference to the mixture of conventional, tactical and strategic forces.

While applauding SALT, Schmidt warned that "strategic arms limitations confined to the U.S. and Soviet Union would be to impair the security" of Western Europe unless something is done about Soviet tactical superiority.

To some Washington officials, the speech implied a German view that Moscow and Washington now had taken care of their own security and the Americans were leaving the Europeans in the lurch. In previous years of acknowledged American superiority in strategic weapons, that might have been acceptable, it was reasoned. But the forthcoming nuclear parity between the superpowers had now changed conditions for Europeans caught in the middle.

Schmidt's speech, to some in the State Department, seemed to carry with it a suggestion that Bonn had lost a little confidence in the long-standing U.S. pledge to come to Europe's defense with its strategic nuclear weapon's against the Soviets if necessary.

Some French strategists formed that Schmidt, by emphasizing the differences between nuclear and conventional weapons, might be encouraging the idea that a conventional attack could take place without nuclear weapons being used to counter attack.

Schmidt has sought to call attention to the discussions he had with Soviet President Leonid Brezhnev when Brezhnev visited Bonn in May and reportedly expressed a willingness to discuss these so-called "gray area" medium-range weapon with the West.

Mixed into this may also be a touch of West German politics. Although nobody here expects Soviet-led forces to come charging over the East-West border, there is concern within Schmidt's coalition government that imbalances in the military situation in Central Europe can be exploited not only by the Soviets but also by opposition conservatives at a time when the German electorate is becoming slightly more conservative. Thus, talk of improving West German security through negotiations is important here these days.

Furthermore, Schmidt, although a major international figure, has no role to play in the U.S. Soviet strategic arms talks but would clearly be a central figure if the East-West bloc discussions in Vienna on mutual troop reductions were to move ahead or if strategic arms talks were to expand in future phases to include the Europeans.

The problem is that weapons such as the new Soviet mobile medium-range missile, the SS20, and the back-fire bomber do not fit into either the SALT talks, which deal with ocean-spanning U.S. and Soviet strategic weapons, or the troop reduction talks, which deal mostly with conventional weapons. Thus, they are called "gray area" weapons.

Bringing these weapons into future SALT negotiations, however, aside from opening up the question of U.S. medium-range jets based in Europe, might also affect French and British nuclear forces, which are medium-ranged, plus other U.S.-developed weapons such as cruise missiles and neutron warheads.

The significance of last month's speech by Defense Minister Apel is that it disclosed a more clearly emerging view in Bonn that the Soviet gray-zone weapons are strategic and should be dealt with in the U.S.-Soviet SALT negotiations.

Apel, a former finance minister who is a protege of Schmidt's and a possible future chancellor, said Europe has nothing comparable to offset the Mobile Soviet weapons directly threatening Central Europe" and that "the explosive strength of these arms has a strategic effect."

The United States shares the German view," Apel said, "that the medium-range disparity is a strategic and thus an arms control problem" and the United States hinted," he added, "that it will seek the solution of this problem in negotiations with the Soviets."