MARGARET WARNER: President Obama landed in Johannesburg, South Africa, this evening, his second stop on a weeklong tour of the continent.
The president's long-planned visit, with his family, comes at a delicate moment, as South Africa's 94-year-old former President Nelson Mandela is clinging to life in a Pretoria heart clinic.
Some South Africans appreciated the timing of President Obama's arrival.
MAN: Mr. Obama's visit will seem to me some form of solidarity, although it may not necessarily be the purpose of his visit. Coming to South Africa at the time the president is ill, and a man so revered nationally and internationally, will, I think, be a very good thing.
MARGARET WARNER: It's unclear if the two men will meet. White House officials said that decision rests with the Mandela family.
Aboard Air Force One en route to Johannesburg, President Obama said he wasn't seeking a photo op, adding: "The main message we will want to deliver, if not directly to him, but to his family, is simply profound gratitude for his leadership."
Mandela remains in critical condition, but his ex-wife Winnie said today there were positive signs.
WINNIE MADIKIZELA-MANDELA, Ex-wife of Nelson Mandela: I'm not here to answer medical questions. I'm not a doctor, but I can say that from what he was a few days ago, there is great improvement, but, clinically, he is still unwell.
MARGARET WARNER: Many gathering outside the hospital appear to be preparing for the inevitable passing of their icon.
TAMMY HACK, Resident of Johannesburg, South Africa: Our hearts are breaking at the moment. He is such an inspiration and he is a true South African hero. I think he is a world hero and we all are absolutely devastated.
MARGARET WARNER: The near quarter-century since Mandela's release from prison and his 1994 election as president brought tectonic change in South Africa. The end of the racial apartheid spurred social and economic development, and catapulted the democracy to the world stage.
The country even hosted Africa's first-ever World Cup in 2010. But for many, dreams of a better life remain unrealized. Income inequality is among the greatest in the world, though some blacks have joined the elite. Crime, corruption, and high unemployment plague the country.
Frustrations boiled over last year. Strikes by platinum mine workers angry with their low wages turned deadly. In one instance, 34 people were killed when police opened fire on strikers. Still, business figures, like this bank analyst, hope the president's visit will boost economic ties between the two countries.
MOHAMMAD NALLA, Bank Analyst: And as the United States emerges from what has been a fairly difficult economic cycle, South Africa really needs to do its bit in trying to cement those relationships, expanding on those trading relationships, because right now our trading relationships with Europe still remain the dominant factor, and we need to diversify some of that over the coming years.
MARGARET WARNER: For now, South Africa continues to struggle in recovering from the global recession. First-quarter growth this year was the slowest since 2009.