As the new chairman of the crisis-ridden Orginization of African Unity, folksy Sierra Leone President Siaka Stevens will have to use all of his legendary persuasive skills to keep the pan-African body from splintering into hostile camps.

Stevens, who will be 75 in August according to his official biography (although others here say he is much older), brings decades of experience to the OAU. Once a simple iron miner, he rose to become a trade union boss and finally a wily, autocratic national leader. For the last 13 years he has outrun, outmaneuvered, outlawed, and, when necessary, crushed his domestic opposition, including coup-plotters, would-be assassins and university students.

With the recent stormy OAU summit finished, the tall, broad-shouldered Stevens relaxed in the living room of one of the 60 villas built here for visiting heads of state and reflected on the challenges ahead.

His most immediate task, he said, is to find a solution to the labyrinth of competing loyalties that have evolved around the four-year-old war in the western Sahara between Morocco and the Polisario Front guerrillas. The issue sparked one of the most acrimonious debates in OAU history at the Freetown summit and spurred 12 countries to threaten to leave the organization rather than accept a majority vote to give the guerrilla group membership status.

The guerrillas won the necessry support of 26 of the 50 member states for admission as representatives of the "independent sovereign state" of the Democratic Saharwi Arab Republic. Some of the votes reflected an anti-Moroccan sentiment that has been growing since King Hassan referred to the OAU as a "tom-tom conference" when it called for a U.N.-supervised plebiscite in the disputed territory.

Stevens, faced with a serious split at the summit, adroitly postponed the guerrillas' technical admission and averted a walkout.

"Not everything that is legal is expedient, so we shelved it," he said candidly about the guerrillas' winning the vote but losing the admission battle. Of Morocco's supporters, he said gaily: "Even the devil has some friends."

Stevens predicted that between now and the next summit "the support for Polisario could grow to 34 or 35 member states" and said the next scheduled OAU chairman, Kenyan President Daniel arap Moi, will not have an easy time shelving the issue again.

OAU efforts to solve another serious conflict, the civil war in Chad, are being frustrated by "outside interference," Stevens said.

"I call it 'political ventriloquism'" he added with a chuckle, but he declined to name the outsiders involved. Reportedly, Libya's leader, Muammar Qaddafi, is supplying troops and arms to one of the warring Moslem factions there.

"We will try [in Chad] again," Stevens said, "but if we fail we will try to get U.N. assistance."

A third divisive question that will continue to test the OAU leader's diplomatic skills is acceptance of the new military government in Liberia, which was responsible for the assassination of former OAU chairman William R. Tolbert.

Stevens spoke with frustration of the meetings he had held before this month's summit with Sgt. Samuel Doe, Liberia's new head of state. Stevens traveled to the meetings in Liberia and the Ivory Coast with three other African leaders -- Guinean President Sekou Toure, Ivory Coast President Felix Houphouet-Boigny and Togo President Gnassingbe Eyadema. p

The four leaders asked Doe to release imprisoned members of Tolbert's family and officials of his toppled government. Some of Tolbert's children and his wife have since been freed.

Stevens intimated, but would not say directly, that the release of the prisoners was contingent on whether the leaders would support Doe's formal seating at the Freetown summit.

"Doe would have had difficulty here" with Nigeria's President Shehu Shagari, one of the harshest critics of the new government, and other African leaders, Stevens acknowledged. Tolbert was the first OUA chairman to be killed while in office.

In April, the Nigerian government would not allow a plane carrying Liberia's foreign minister to land at Lagos and attend an extraordinary OAU economic summit. Nigeria also led the successful move to unseat the Doe-led Liberian delegation to the 16-member Economic Community of West African States summit in Lome, Togo last May.

Doe's coup overthrew the tightly knit oligarchy of Americo-Liberians, descendants of former slaves from America who settled the country and ruled Liberia since 1847. The coup was followed by the brutal executions of 13 former Tolbert government officials, all Americo-Liberians. The executions caused widespread revulsion, and at least one group the European Economic Community, immediately suspended its aid program.

"We suggested that they cut out the witch hunt," Stevens said. If they killed all the Americo-Liberians, Stevens said he told Doe, "you won't have people to run the country."

But Doe is not in full control and is answerable to the all-military, 28-member People's Redemption Council that he chairs, Stevens said. When the leaders asked for the releases, Stevens said Doe replied, "I cannot do all these things myself. If I do, I'll get into trouble.'"

"Houphouet-Boigny told me that the foreign minister is a hostage," Stevens said. "Even Doe is a hostage," he added. "Anything can happen there."

Although American Vice President Walter Mondale is due to tour Africa next week, Stevens said he feels the United States "does not think much" about Africa.

"There is no consistency" in American policy, he said.

Africans continue to be suspicious of the United States, he said, because of its record of involvement in the downfall of the Salvador Allende government in Chile and the CIA-backed coup that brought the ousted shah of Iran back to power in 1953.

Stevens even had his doubts about the freedom of news reporters in the United States.

"I don't know about your system," said the man who keeps his press under tight reins. "The president [of the United States] can't go to the bathroom without everyone knowing about it."