The European mood, now approaching panic over President Carter's proposed strategic-arms agreement with Moscow, is beginning to infect even this stronghold of Gaullist arrogance, with damaging implications for Western unity.

President Valery Giscard d'Estaing, long a stranger to the science of modern weapons, is now on a self-imposed crash study progam with top aides. The purpose: to prepare the French case against the new American policy described to us by one of the highest officials here as "de-coupling U.S. security from European security."

That France, so long the aloof stranger to NATO military cooperation, is entertaining such fears might seem perverse poetic justice. In fact, however, France has always been afraid that, when the game of hardball started, the United States would choose strategic "security" with the Soviet Union over its European alliance.

The fact that Jimmy Carter now seems determined to make the French nightmare come true by denying Western Europe access to medium-range cruise missiles simply proves to the French how right they were.

"It is not just the limits that we understand are being imposed on the ground-launched cruise missile," one top-ranking policymaker told us. "Previously, negotiations between Washington and Moscow were aimed at a balance, with protection also for Western Europe. The new negotiations are acquiring a dynamic that tends toward apparent parity for the two superpowers while ignoring Europe."

Should this assessment prove correct, he said, "a turning point in postwar history will soon be reached because the Soviets would draw the conclusion that Western Europe is open to them." He did not mean necessarily military invasion but rather the political and economic impact of overwhelming Soveit military superiority in Central Europe.

American diplomats are skeptical of French sincerity in privately expounding this line. They also claim that West German Chancellor Helmut Schmidt, in his recent warning delivered in a speech to the Institue of Strategic Studies, was uninformed.

Correct or not, there is solid reason to believe that Carter underestimates European alarm about his pending strategic-arms deal with Moscow. the brutal truth is that Carter's top SALT planners are regarded here, as well as in Bonn and London, with skepticism or something much worse.

That skepticism goes far beyond SALT and the dilemma it is creating for European acquisition of new weapons to defend against the awesome Soviet buildup of nonstrategic fighter aircraft, nuclear missiles, dense antiaircraft systems, tanks - and now the Backfire bomber. ("The Backfire is terrible, you say, so let it only be able to strike Europe," one middle-level planner told us in a revealing sarcasm.)

The problem as seen here, however, goes deeper, starting with heightened Soviet penetration into Africa. When the French sounded out Washington on the Soviet-backed Angolan incursion into Zaire, the answer was nonchalant: Zaire's President Mobutu Sese Seko was not worthy of U.S. help.

Only then did France and Morocco decide to team up in a successful rescue operation later applauded in Washington. But U.S. reluctance to block the extraordinary Soviet absorption of Ethiopia is worse, as seen here. A French sounding for taking Moscow's intervention to the United Nations fell flat in Carter's State Department: Western intervention would be affront to African states (despite dispatch of an estimated 2,000 Soviet tanks as part of $300 million in military aid to Addis Ababa).

Senior French officials view Ethiopia as the most significant Soviet move yet to secure a Red Sea base as a strategic pivot on Persian Gulf oil, Supine U.S. reaction has but one explanation here: desperate urgency for SALT II.

These were to have been the central topics Giscard d'Estaing would take up with Carter this month. With the French election in March, no Carter visit is possible after the first week in January. Thus, gnawing French grievance over U.S.-Soviet limits on European cruise missiles and the declining state of Carter's credibility will worsen, perhaps to a point of agony for both Paris and Washington