French confident about Libyans in Chad

French troops begin withdrawing from Chad last week. Libyan troops did not, and French officialssay they don't trust Libyan leader Muammar Qaddafi's promise to keep his troops out of the African country even if the planned simultaneous withdrawal of foretroops is completed as scheduled in one month's time.

Yet the French say they are not worried. Libya has not broken the agreement, say French officials, who remain confident in their ability to control Colonel Qaddafi's moves in the area.

''We will be able to observe his movements by air and return quickly if the Libyans return,'' says a top advisor to President Francois Mitterrand.

Air surveillance is key, the French say. Although Chadian President Hissein Habre has denounced the Franco-Libyan agreement and refused to let a pan-African observation force monitor the withdrawal, the French will continue flying sorties to ''keep track of the Libyans.'' If a Libyans don't leave, or if they advance southward, the French say they would immediately move troops based in neighboring African countries back to the front line.

''We never counted on the observers in the first place,'' the official said. ''It's our planes that count.''

Because of this aerial insurance, the French discount criticisms expressed by the United States and Mr. Habre's government that the risks outweighed any potential benefits of negotiating with Qaddafi.

When Libya moved into Chad in August 1983, the French responded by sending 3, 000 troops. They announced that they would attack only if Libya kept moving south and challenged them. The Libyans stopped.

''Qaddafi understands force,'' a French official explains. ''I would have thought that the Americans, who pride themselves on being pragmatic, would have been able to see this.''

Moreover, the French believe Qaddafi has practical reasons to withdraw at least temporarily. They say he was finding the occupation of northern Chad expensive at a time of falling oil revenues. He has also been hurt by the crumbling of his Chadian allies. The French say many rebel soldiers have deserted recently and that the groups' chiefs have been squabbling.

Perhaps most important, the French think the Libyan Army was becoming increasingly disillusioned about being in Chad.

''The Army is Qaddafi's principal internal threat,'' says one official. ''If Qaddafi is to be overthrown, it will be by the soldiers.''

The situation inside Chad is even more fragile. As soon as the French and Libyans withdraw, President Habre will probably try to reoccupy the north.

The French believe Habre might just be able to consolidate his power. Rebel forces note that Habre has recently widened his Muslim power base by taking southern, Christian leaders into his government.

The French plan to help Habre consolidate his power. They will continue to train his Army. They have also invited him to visit Paris.