The risk of a full-scale war between France and Libya in growing in the divided African nation of Chad. Following last week's raid by Libyan-backed rebels from their base in northern Chad and the downing of a French Jaguar jet, French forces moved their front lines about 60 miles north over the weekend.
The action puts French President Francois Mitterrand into the tensest face-off with Col. Muammar Qaddafi's Libya since French forces returned to the former colony during the conflict that erupted six months ago.
The French also tripled their Air Force contingent to more than 24 planes in Chad, according to military officials here.
In response to these moves, a spokesman in Paris for Chadian rebel leader Goukhouni Woddei accused France Sunday of ''throwing oil on the fire,'' and asked the Libyans for direct military intervention.
On Monday, Libya's charge d'affaires in Paris said his government was studying the rebel request.
The new French jets may indeed escalate the conflict. They may be used for retaliatory air strikes, the Defense Ministry officials said. In addition, orders have been given to French ground forces ''to engage any hostile force'' that enters the new, extended security zone.
''We reserve the right to strike where we want,'' one high-level French Defense Ministry official said. But what this exactly means remains unclear. Will the French sit behind their new lines? Or will thay attack the main Libyan stronghold at Faya-Largeau, now only about 100 miles south of their forward troops?
The usually authoritative Le Monde reported over the weekend that French forces were now determined ''to make Tripoli retreat.'' Only violent sandstorms in the war zone prevented immediate French retaliation, the newspaper said.
But French Defense and Foreign Ministry officials suggested to the Monitor that a concerted offensive against the Libyans would probably not be ordered until there was another provocation.
''The ball is in the Libyan court,'' one official said. ''They must now choose whether they want a solution or a confrontation.''
Still, just by waiting, the French acknowledge that the risks of a confrontation grow. Until last week, the 3,000 French troops deployed in August across the center of the country had not fired a single shot. Their mere presence had been sufficient to stop the fighting.
The French hoped this military stalemate would push Goukhouni's rebels and the government of Hissein Habre into negotiating a solution. But after months of buildup, a peace conference scheduled earlier this month in Addis Ababa fizzled.
This set the stage for last week's rebel surprise attack on a Habre government outpost, Ziguey, south of French lines. Although the Libyans continue to deny that that they have any forces in Chad, the French blamed them for the attack, saying that at the very least, Libya had made the attack possible by supplying the rebels with about 20 armored vehicles.
So the French sent their Air Force into action. Two Jaguar jets succeeded in destroying two-thirds of the rebel columns. ''A good dozen of their vehicles were put out of action,'' a French Defense official said. But the rebels brought down one of the Jaguars, killing its pilot, with what French officials believe was automatic rocket fire.
Angered, and also a bit embarrassed, the French reinforced and moved their forces forward. Their new positions put them in danger of direct contact with the rebels, and not far from Faya-Largeau where the French say the Libyans have reinforced their garrison to a total of 6,000 men. Even more ominously, for the first time Libyan fighters based in southern Libya or in the contested Aozou Strip can reach the French forces.
So tension is mounting. And the French, caught in the middle, cannot back down. Although French officials have said privately that they would allow their forces to fight directly with the Libyans, they would still prefer to negotiate an end to the conflict.
On Monday, the French government announced that External Relations Minister Claude Cheysson will travel to Ethiopia, Libya, and Chad this week to search for a solution. But privately French officials are not hopeful.