When Vice President Bush expressed the Reagan administration's concern over the inclusion of four Communists in the new French cabinet, and President Francois Mitterrand told the United States to mind its own business, both men were performing a political ritual as formalized and artificial as a minuet. In private, Mitterrand is staunchly pro-American, and his dependability as an ally was not compromised by naming Communists to four posts in his 44-member cabinet.

The Pentagon and CIA have begun reviews of the implications of the Socialist victory in France. But the CIA's experts -- who predicted Mitterrand's election -- are not surprised at the Communist appointments. The history of Mitterrand's use -- and abuse -- of the French Communists goes back -- to 1972. The polls showed Socialist Party strength at a pathetic 15 percent, five points below the Communists. Mitterrand engineered a merger in the form of a deliberately generalized "common program for governing."

As a secret CIA analysis observed, the Socialist party grew "rapidly at the expense of its Communist allies." By the 1978 legislative elections, the Socialists had nearly doubled their strength, winning 28 percent of the electorate; the Commuists hadn't budged from their core of 20 percent.

Mitterrand "played down favorable attitudes toward such issues as NATO and European integration in order to expand [the Socialists'] constituency to the left," the CIA noted. The strategy worked.

But Mitterrand was concerned that his apparently anti-American position might be misinterpreted on this side of the Atlantic. He dispatched an emissary, the Socialist party's international secretary, Robert Pontillon, to the American Embassy to ally U.S. misgivings, in case the Socialist-Communist coalition won the 1978 elections.

My associate Dale Van Atta has seen the cables the embassy sent to Washington about Pontillon's secret mission. The cables spelled out Mitterrand's insistence that his reassurances not be made public. Pontillon, according to once cable, "informed Embassy Paris that; Mitterrand is concerned about the U.S. security commitment to France and wants assurances that the U.S. would maintain its defense umbrella is a Socialist-Communist alliance come to power. . . ."

At a meeting the American Embassy, according to a top-secret cable, a "leader of the French Socilist Party . . ." -- probably Pontillon -- "said that the Socialists still believe France ought to seek West Eropean integration and remain in NATO. He added that the party leadership is preoccupied with European security, which 'we understand can be found only through a privileged relationship with the U.S.'"

The Socialist offical told the Americans that, if his party came to

The Socialist offical told the Americans that, if his party came to power, France would continue to work with NATO, though not as part of its integrated military command.

Current intelligence analyses suggest that Mitterrand has succeeded in mousetrapping the Communists. By giving them four relatively minor cabinet posts, he has bought their allegiance, however reluctant. He has also ensured labor peace, since his Communist allies control France's largest union.

Mitterrand appears to have achieved the best of two worlds -- an opening to the left and a backstop from the United States.