What was supposed to be the foreign policy triumph of Francois Mitterrand's presidency has turned into a diplomatic botch so large that it threatens to strain the generally excellent relations between France and the United States.
Mr. Mitterrand met with Libyan leader Muammar Qaddafi last week and then admitted that 800 to 1,000 Libyan troops remain in Chad - in complete contradiction of earlier French statements that the Libyans had completed their withdrawal as scheduled in a French-Libyan agreement in September.
Over the weekend, the French reaffirmed their military presence by sending their Jaguar jet fighter-bombers on missions over Chad. Defense Minister Charles Hernu and Army Chief of Staff Gen. Jeannou Lacaze flew to the Chadian capital of N'djamena, lending support to television reports here that French troops would soon return to Chad.
Most ominous of all, French officials were suggesting privately that French troops would go on the offensive if they returned, not merely act as a dissuasive force as they had in the past.
But these actions and threats have not stemmed the damage from the foul-up at home and abroad.
Relations with Washington are one casualty. Early last week the Americans embarrassed President Mitterrand by announcing that Libyan troops had not withdrawn while the French government was insisting they had.
Mitterrand, in turn, angered the Americans by meeting with Colonel Qaddafi. The French President and his spokesman, Roland Dumas, told reporters that US efforts to pressure its allies into confronting the Libyan regime were hypocritical while the US maintains strong trade relations with Tripoli. On his way to Washington Sunday for a two-day visit, Foreign Minister Claude Cheysson said, ''The Americans' desire is to show that their manner of pressuring Nicaragua is good and therefore we must act the same way with the Libyans.''
France's African allies might appreciate it if Paris acted more like Washington. The Africans fear Libyan destabilization.
They look to the French for defense and view French support of Chadian President Hissein Habre as a test of their protector's will. But in their haste to pull out, the French did not reassure their allies.
At home, too, the controversy could hurt Mitterrand badly at a moment when his standings in the polls were already at an all-time low. In the past, the President had escaped serious criticism of his foreign policy at home. Now he is being portrayed as foolish.
''The French government lied,'' headlined the opposition Le Quotidien. Even Le Monde, the respected daily that usually favors the government, called the affair ''the regime's biggest gaffe yet in foreign policy'' and asked pointedly, ''Why state that the Libyan evacuation was finished when it wasn't?''
The answer to that question remains unclear. In public statements, neither Mitterrand nor Dumas explained why optimistic claims had been put forward in the first place.
Mitterrand said the Libyan withdrawal proceeded normally until Nov. 9, when French intelligence noted ''a slowing down.'' He added that Qaddafi had assured him at their meeting that ''everything was ordered for a total evacuation.'' But the President specified no time limit.
Why is Mitterrand giving Qaddafi, who has been shown to have broken his word, another chance? The French suggest that the US policy of isolating Qaddafi only encourages more Libyan adventuring. Better, the French say, to offer him the possibility of improved relations with Paris if he refrains from causing problems in North Africa. The French figure that, rather than face an offensive French force, Qaddafi might finally pull the rest of his troops out of Chad.
French concern over North Africa is mounting. Libya has upset the balance of power there by moving closer to Morocco. Tunisia's President Habib Bourguiba is reportedly ailing, and officials here question Algeria's stability.
With such a volatile situation, Mitterrand justified his meeting with Qaddafi as a means ''to emphasize the legitimate demands of France.''