Rock 'n' roll stars perform in his honor. Archbishop Desmond Tutu calls him "my leader." Publishing his picture is illegal in South Africa, but even toddlers chant his name.

Nelson Mandela, who turns 70 on Monday, is arguably the world's most influential prisoner. Although jailed since 1962, he is the most admired leader among South African blacks, the embodiment of their quest for political freedom.His birthday, celebrated by protest marches and rock concerts overseas, has reminded the government of the legions of people worldwide who want him released. Blacks spanning South Africa's ideological spectrum, as well as many whites, say no political breakthrough can occur while Mandela is behind bars.

"Nothing the South African government can do will gain credibility while it treats Dr. Mandela as a dangerous enemy," Zulu leader Mangosuthu Buthelezi said in a recent speech. "Black South Africa will not rest until he is free."

Buthelezi is a bitter foe of the African National Congress, the outlawed guerrilla movement Mandela led from underground prior to his imprisonment. But Buthelezi, like other blacks who oppose the ANC's strategy of violence, sets Mandela apart and discusses him with deep respect.

President P.W. Botha's government has considered the idea of freeing Mandela, and several times in recent years there were flurries of speculation that his freedom was imminent. One such period came last November when authorities freed Govan Mbeki, one of seven ANC leaders sentenced along with Mandela to life prison terms in 1964 for plotting a sabotage campaign aimed at overthrowing white-minority rule.

The speculation was swiftly dampened when police imposed severe restrictions on Mbeki. Since then, government officials have indicated Mandela's release is unlikely unless he publicly renounces violence - a condition he rejects unless the ANC is made legal and apartheid dismantled.

When convicted for sabotage, Mandela already had served two years in prison, having received a five-year sentence in 1962 for incitement and leaving the country illegally.

He spent the first 18 years of his life sentence on Robben Island in Cape Town's Table Bay. He was transferred in 1982 to Pollsmoor Prison in Cape Town, where he is reported in good physical and mental health.

Mandela reads uncensored newspapers and is expected to earn an advanced law degree later this year through correspondence courses. He was a practicing lawyer before he went underground and has been awarded honorary doctorates from various universities during his imprisonment.

He reportedly has a spacious cell with access to a rooftop garden.

The government has given permission to Mandela's family to have a six-hour reunion with him Monday at Pollsmoor, by far the longest such meeting since he was jailed.

Mandela's wife, Winnie, has asked that the birthday be observed "as a day of peace, in line with the peaceful struggle we have always tried to maintain."

She has not commented publicly about the recent series of bombings of civilian targets in South Africa - attacks South African police officials blame on the ANC.

Nthato Motlana, an anti-apartheid activist from Soweto and an ANC member before it was outlawed in 1960, said Mandela seeks to avoid civilian casualties.

He resorted to a strategy of sabotage in 1961 "because all other avenues were exhausted," Motlana said. "He is the one man who, assuming he is willing, could lead us out of this mess."

Buthelezi also views Mandela as a potential peacemaker, as perhaps the only person capable of ending a bloody power struggle in Natal province between militant ANC supporters and more conservative blacks who follow Buthelezi.

"I believe he (Mandela) would come out of jail to thump anybody . . . who set black brother against black brother on the eve of a final victory over apartheid," Buthelezi said.

Some South Africans believe Mandela causes more trouble for the government in jail than he would if freed. Some warn of a violent black backlash if he dies in prison.

The largest daily newspaper, The Star, recently urged Mandela's release on pragmatic grounds. It said in an editorial:

"Should Mandela die in prison, he will be accorded universal political canonization and Pretoria will attract even more censure. Once he is free, the Mandela myth would be cut down to size"

The world hears from Mandela himself primarily through past statements which relatives and colleagues continue to quote.