Despite intense Africa-wide public and diplomatic pressure, Nigeria has been unable to end the unnerving presence of thousands of Libyan soldiers on its northern borders in Chad.

Nigeria and other African states that border Chad view the Libyan military presence as potentially destabilizing in their own fragile domestic situations. The penchant of Col. Muammar Qaddafi for disturbing the poltical tranquility of his neighbors has left Libya increasingly isolated on this continent but apparently has not stilled the radical Libyan leader's dreams of a western and central Africa vibrating to the pan-Islamic themes he has tried to export from Libya.

Nigeria takes the Libyan presence in Chad so seriously that it has recently reinforced its Borno State border with a number of its own troops amid reports of armed clashes there between Nigerian soldiers and armed Chadians crossing into Nigeria across the narrow Cameroon corridor that separates the two countries.

So far, the one tangible Libyan reponse to Nigerian pressure and demands of the Organization of African Unity written by Nigerian President Shehu Shagari was a public retraction eariler this year of announced merger plans with Chad. But in a major speech earlier this month, Qaddafi seemed to reiterate his intention to go ahead with the merger without saying so directly.

"We declare that the fate of the Chadian people and that of the Libyan people has become one common fate forever," Qaddafi said.

In addition, he charged that those against the merger are "racists, filthily working for the destruction of African unity." This was seen particularly as an attack on France, which as Chad's former colonial owner has taken a special interest in the issue.

"We tell France and the whole world," Qaddafi continued, "that Chad is linked to Libya, Libya to Chad, by destiny, geographically, humanly, historically, futuristically, by security and economically."

Qaddafi's green-uniformed troops intervened in Chad last fall at the invitation of President Goukouni Oueddei and in mid-December led guerrillas of Oueddei's splintered transitional government in crushing a nine-month-old rebellion by one of Chad's 11 guerrilla armies.

For 15 years of its 20-year independence, Chad has been riven by civil war. The OAU proposals include dispatch of a peacekeeping force to replace the Libyans and try to keep a damper on any further fighting between the factions until free elections can be held to establish a permanent government.

A widely anticipated face-to-face meeting among Qaddafi, Oueddei and Shagari failed to come off in February because Libya did not respond to Nigerian demands that only the timetable for a Libyan troop withdrawal be discussed.

Chad's apprehensive Oueddei had lobbied hard for the meeting, said Nigerian Foreign Minister Ishaya Audu. Oueddei was worried that two of Africa's richest countries, which could most afford to assist Chad in reconstruction, would be unwilling to work together.

Libyan diplomats here were expelled after announcing in early January that they were converting their embassy to a "people's bureau." But the 48-hour expulsion order came a day before the Libya-Chad merger announcement on Jan 6, not simultaneiously had in reaction to the announcement as had been previously reported.

Audu insists that Nigeria and Libya are "not at loggerheards." Diplomatic relations between the two countries have been broken, he added, and any day they want to come and open a proper embassy they'll be received; they'll be welcome really."

Other high Nigerian officials are not so sanguine.

"We believe Oueddei is at the mercy of the Libyan's" said one of Shgari's staff. "The Libyan argument of moving into Chad to keep the French out has some credibility but now they must move out as well. One would like an expression of their willingness to move out and they have not done that."

French-speaking countries with borders with Chad, like Niger and Cameroon, are unwilling to rely completely on military assistance from France and are leaning increasingly on Nigeria, said several well-informed sources. At the end of January, the defense staffs of the three countries held an unprecedented meeting in Lagos.

"France was slow to respond to the Libyan involvement in Chad while she was at the same time negotiating an oil exploration contract with Libya," said a French-speaking diplomat here. "We don't know if we can trust her."

Yet even with the larger standing army -- Nigeria has some 150,000 troops under arms compared to Libya's 35,000 -- the Nigerians "would be hard-put in any head-on battle with Libyans and their sophisticated equipment," said a Western analyst.

Libya has built up an impressive war machine with massive arms purchases from the Soviet Union and warplanes from France. For now, however, Audu concluded, the Nigerians are waiting to hear what the next step of Qaddafi and Oueddei will be.