Chad's military drive to expel Libyan troops from northern Chad has quickly escalated into an international affair. Calls for help from Chadian President Hissein Habr'e are drawing both the United States and France into greater involvement in the dispute. Their involvement is putting Libya against a more powerful foe than it has faced up to this point.
Chad claimed yesterday that its ground forces were pushing back the Libyans and their rebel Chadian allies after repelling Libyan air and land assaults. Action has spilled over into the Libyan-administered Aozou Strip of northern Chad, occupied by Libya since 1973.
Concern in West European capitals increased when the news emerged of what the West German magazine Stern reported in today's issue: that West German rocket and electronics firms had helped Libya develop a guided missile with a range of more than 300 miles. Its testing ground lies in the southern desert of Libya near the Chad fighting, Stern said.
Last week, the Reagan administration decided to rush $15 million in military aid to Chadian forces and their formerly pro-Libyan tribal allies, many of whom recently joined Chad's 12,000-man Army.
French commanders of the 1,200-man French land and air forces stationed in Chad ordered air drops of equipment to the Habr'e forces, but have so far resisted President Habr'e's pleas for direct intervention. Diplomats in Europe say they believe the Reagan administration, welcoming the diversion from the Iran-contra affair, is pressing France to aid Chad in a drive against the well-armed Libyans.
The US failure to neutralize Libyan leader Muammar Qaddafi in last April's air attacks on Libya has redoubled the Reagan administration's zeal to see ``Qaddafi's nose dragged in the African mud'' through defeat on his exposed southern flank, European analysts say.
Though intended to punish the Libyan leader for supporting terrorism, the April attacks actually strengthened him by at least temporarily rallying the Libyan forces to defend against US ``aggression,'' these analysts say. Many analysts believe there is concern in Libya over Army discontent generated or launched from Chad - as it was in a 1970 coup attempt.
Libyan radio broadcasts last weekend suggesting that the Soviet Union ought to help defend Qaddafi's position in Chad and accusing the US and France of ``aggression'' betray Qaddafi's sensitivity to a ``southern threat,'' the analysts say.
Qaddafi's latest troubles in Chad arise from a switch of loyalties among tribes in Borkou, Tibesti, and Ennedi, Chad's northern desert and mountain regions.
Goukhouni Woddei, a northern tribal chief and former president of Chad, was Libya's chief ally in Chad as head of the dissident Transitional Government of National Unity (GUNT). With Libya, he opposed Habr'e, also a northern Muslim.
Mr. Woddei is now a prisoner in the Libyan capital, Tripoli. He was reported wounded in October while trying to escape Libyan captors during a visit there. Except for a small group led by Omar Asheikh, most of Woddei's men have turned against Libya.
Fighting the US-backed Chadian forces are the regular Libyan Army and Air Force, and Qaddafi's ``Islamic Legion'' of ``volunteers'' - Africans and others pushed into Libyan service.
Unless France uses its Air Force, which President Fran,cois Mitterrand is reluctant to do, Chad faces Qaddafi's Air Force with virtually no air cover.
Habr'e's offensive is sparked partly by a desire to rectify frontiers imposed unjustly or arbitrarily by colonial powers.
In 1935, when Chad and Libya were still French and Italian colonies respectively, France and Italy signed a treaty. It moved the Libyan border with Chad about 65 miles south. The area given to France was the so-called Aozou Strip. Bardai, its capital and main Libyan headquarters, is one apparent objective of the new Chad offensive.
France never ratified the 1935 agreement and no Chadian government has ever recognized it. But the dissident GUNT accepted it.
In 1980, Qaddafi's forces moved south from the Aozou Strip and occupied much of Chad. The Libyans eventually pulled out and an African peace force moved in briefly. But by the end of 1982, Habr'e's allies had control of most of the country. In January of this year, Woddei's forces, closely backed by the Libyans, again attacked towns south of the 16th parallel, established by France in 1983 as a ``red line'' Libya must not cross.
On Feb. 16, French Jaguar fighter bombers attacked and damaged the Libyan airstrip at Wadi Doum. The French airlifted about 750 hand-picked troops from Central African Republic bases to N'Djamena, the Chadian capital. This served notice to African allies that France would observe its defense agreements with them. It also signaled to the Reagan administration that France had not ``gone soft'' on Qaddafi. In the past, France and Qaddafi have preferred to deal with each other rather than with Chadian surrogates in seeking a settlement.
John Cooley, a former Monitor correspondent, is an ABC News staff correspondent based in London who has written ``Libyan Sandstorm'' and other books on North Africa and the Mideast.