The leaders of France and West Germany started three days of meetings today to define a joint policy toward the United States.

It has become increasingly apparent that the overriding concern of French President Valery Giscard d'Estaing and West German Chancellor Helmut Schmidt is not so much how to respond to the Soviet invasion of Afghanistan but how to respond to President Carter's demands for strong anti-Soviet retaliation.

Schmidt, whose unenthusiastic views toward Carter are well known in Europe, is said by those who have been tracking him lately to be privately very worried and critical of the U.S. president's latest initiatives.

Before becoming involved in what he called a "deadly game" against the Soviets, Schmidt told a recent visitor that he wanted to know what Carter's strategy, aims and means are. The chancellor said a dialogue would sooner or later need to be reestablished with the Soviets and he wanted to know how Carter proposes eventually to do that if he continues his present course of closing off contact and discussion with the Kremlin.

Giscard d'Estaing, who is known to share Schmidt's basic concerns, is neverless said by French sources to be resolved to temper his West German friend's concerns. The French view is that America's reawakening to its world leaderhsip role is a basically healthy thing that should not be discouraged.

Once the Amercians understand that the allies are basically with them, despite the considerable public and private reservations they have expressed, Giscard is understood to argue, there will be time enough to get Washington to correct what are viewed as overreactions like the demand for a boycott of the Olympic Games.

Schmidt is said to be particularly dismayed by the new Carter doctrine for the Persian Gulf on the ground that the United States does not currently have the local military power availaable to wage a successful conventional war there against a Soviet adversary with the advantages of being able to deploy and supply its forces from inside its own nearby frontiers.

Schmidt also has said he believes the U.S. posture is undermining promising Western diplomatic and economic initiatives in the region.

Schmidt has underlined the importance he attaches to the talks in Paris by setting Giscard to double the time allotted. The occasion is the 35th semiannual Franco-German summit, originally scheduled to start Monday afternoon. Schmidt brought along an unusually large contingent of 11 Cabinet ministers, including, for the first time in several years at such a meeting, the defense minister.

The two governments plan to end the meetings on Tuesday with a joint declaration. French sources say they recognize that it should include stronger language than heretofore condemning the Soviet invasion, if only to avert a crisis with the United States. But the French aim is also to include a strong reaffirmation of the attachment of the two leading West European continental allies to the pursuit of detente with the Soviets.

This is a key West German goal -- along with a more coordinated European strategy for containment of Soviet influence in the Persian Gulf and Asia, that more clearly outlines roles to be played by the United States and the Europeans.

The Franco-German meetings follow remarks here by former interior minister Michel Poniatowski, one of Giscard's few political intimates, that Europe should form its own independent nuclear force and let the two superpowers commit mutual nuclear suicide, an expression of potential French neutrality that created dismay and disarray in the French defense and foreign policy establishment and that also left West German officials expressing private concern.

The reaction, expressed in very strong terms behind the scenes, apparently led Giscard to say in a French provincial speech yesterday that working for peace "does not exclude loyalty toward alliances nor firmness in our positions."

The French government nevertheless seems to be backtracking on its initial opposition to the Olympics boycott in response to its own public opinion. Sports Minister Jean-Pierre Soisson let it be known after a luncheon with Giscard last week that France's position is now "Olympics yes, Spartan Games no," indicating that if France found itself to be one of the few countries outside the Soviet Bloc going to the Moscow games it might pull out. The intrabloc athletic competition held last year in Moscow was called the Spartakiade.

Meanwhile, former U.S. secretary of state Henry Kissinger issued warnings here against the Schmidt-Giscard position. Kissinger saw Schmidt recently and sees Giscard frequently.

"I do not believe," said Kissinger in a radio interview, "in divisible detente in the sense that one side does the defense and the other side does the negotiating and America should do the arming, that Europe should have a monopoly on detente and America a monopoly on defense." Nor, he said, does he accept that "France should have the monopoly on moderation and the United States the monopoly on belligerency."