ADDIS ABABA, ETHIOPIA, SEPT. 11 -- Chad and Libya today agreed to a cease-fire brokered by the chairman of the Organization of African Unity.

The surprise agreement, which follows some of the bloodiest fighting ever in the long-running border war between the two countries, was announced here in the Ethiopian capital by Zambian President Kenneth Kaunda, the current OAU chairman.

Kaunda said the cease-fire, which went into effect at noon today Libyan time, followed his recent meetings with Col. Muammar Gadhafi in Libya and with President Hissene Habre in Chad.

"In both countries I was assured that the two leaders were very much interested in genuine peace and in finding a solution to their problems peacefully," Kaunda said.

Today's agreement seems to be in line with French, not American, policy in the region.

In recent months, France has objected to the growing aggressiveness of Chad, its former colony, which is backed by French troops and receives arms from the United States. The French government has insisted on international mediation rather than military action to settle Habre's claim to Aozou Strip. The 600-mile-long, 60-mile-wide stretch of desert has been at the heart of sporadic fighting since 1973 when Libya annexed it from Chad.

The United States, however, has supported Habre's insistence that the strip belongs to Chad. Washington expressed understanding last week of a Chadian attack on an air base 60 miles inside Libya.

Foreign Minister Jean-Barnard Raimond said this week that French, not American, policy is best for the interests of Chad and the rest of Africa. Raimond and other French officials have made it clear that they disapproved of the Chadian attack inside Libya and of strikes against Libyan troops in the Aozou strip.

French analysts in Paris suggested today that the United States wants to see Gadhafi punished while the French are more interested in preserving their influence across the region.

Libya charged this week that the United States had supplied Chad with "large quantities" of Stinger antiaircraft missiles.

{In Washington, a Pentagon spokesman, asked about the Libyan claim, said, "I can tell you that the Defense Department has not provided Stingers to Chad." Another U.S. official said, "There are no Stingers there {in Chad} that are ours."

{However, the Pentagon spokesman confirmed that the United States has sold Stingers to France. There have been no reports of any French provision of the U.S.-made missiles to Chad.}

Chad appeared this year, for the first time, to have gained the upper hand in the war.

Beginning in January, Chadian troops humiliated Gadhafi's government with a series of decisive victories that pushed the Libyan military out of Chadian territory.

Emboldened by its success, Chad moved into the Aozou Strip in August. Its forces were repulsed by a Libyan counterattack. But last week Chad again went on the offensive, attacking the air base at Matan as Sarra in Libyan territory. Chad claimed that its troops killed 1,713 Libyan soliders and destroyed 28 aircraft.

On Monday French forces shot down a long-range Libyan bomber over the Chadian capital of Ndjamena.

The French armed forces chief of staff, Gen. Jean Fleury, flew to Ndjamena this week after the downing of the Libyan Tupolev 22 bomber. Although his message to Habre was not disclosed, officials in Paris pointed out that French troops are based in Chad only for the protection of the southern part of the country, not to serve as logistics support for Chadian offensives.

Official Chadian radio, in announcing the cease-fire today, warned its citizens to be on the lookout for Libyan air attacks. This week Libyan warplanes have conducted several raids in northern Chad.

Chadian radio reported more bombing this morning, but it was unclear whether it occurred before or after the cease-fire went into effect. The radio also said acceptance of the cease-fire did not mean that Chad had renounced claims to the Aozou strip.

The official Libyan news agency, JANA, said Libya was stopping its "punitive" air raids inside Chad in response to "pressing and repeated appeals" from Kaunda.

The OAU chairman said the cease-fire had been agreed to "with no prior conditions" by either Chad or Libya. Both countries, he said, have promised to maintain their current positions in the Aozou Strip.

Kaunda said an ad hoc OAU committee on the Chad-Libyan dispute will meet in the Zambian capital of Lusaka Sept. 24 or 25 "to find permanent solutions." He said he hoped that both Gadhafi and Habre will attend the meeting, which is to be chaired by Gabon's president, Omar Bongo.

"In my message {to Chad and Libya}, I told them to stand where you are, don't move . . . hence the urgency of this meeting," said Kaunda.

In past years, many African countries quietly had supported Habre's fight to push Libyan soldiers out of northern Chad.

But with last Saturday's attack inside Libya, several countries urged restraint and called for peace talks. Algeria denounced the attack on the Libyan air base as a violation of Libyan territory.

The borders of many African governments are threatened by rebel groups, and leaders on the continent, fearing that they may one day be threatened, are quick to disapprove of any cross-border incursions.

Besides meeting with the approbation of several members of the OAU, today's cease-fire affords Gadhafi a graceful way out of a war that his soldiers, despite superior weapons, appeared to be losing.

In the spring of this year, Libyan soldiers appeared ill-organized and reluctant to fight as they were chased out of Faya Largeau, the oasis that is the administrative capital of northern Chad.

Washington Post correspondent Edward Cody in Paris and staff writer David B. Ottaway in Washington contributed to this report.