US Secretary of State Hillary Clinton poses with Nelson Mandela and his wife Graca Machel at his home in Qunu.
Her private lunch with the Nobel Peace Prize winner, the first event of her South African visit, is an honour that few receive as Mandela's health has become more fragile with age.
Mandela did not speak but smiled as he and his wife Graca Machel posed for a picture with Clinton inside his home in the village of Qunu, in rural Eastern Cape.
"That's a beautiful smile!" Clinton said.
"Madiba's smile is a trademark," Machel added, using Mandela's clan name.
Mandela was elected president in South Africa's first all-race elections in 1994, after spending 27 years as a political prisoner under the segregationist apartheid regime.
Clinton's husband, Bill Clinton, was the US president when Mandela took office. Their two families developed close ties, with Bill Clinton paying a visit to Qunu last month on the eve of Mandela's 94th birthday.
'Close friend'
"Madiba not only represents all that there is great in the world, but [is someone] who to the secretary is a close friend … somebody who she has learned a lot from," a US official said ahead of the top US diplomat's meeting.
A dozen police stood guard outside the homestead. As the town is long accustomed to high-profile international guests, Clinton's motorcade attracted little attention as it rolled through.
Hillary Clinton last met Mandela almost exactly three years ago at his Johannesburg home, when she praised the influence that he had on her own life.
"It of course inspires in me an even greater admiration for his public work but an even greater affection for the man," she said after viewing the mementoes in his home in August 2009.
She also hailed the "discipline that he brought to a life filled with so many great achievements, not only for him personally but for South Africa and the world".
After meeting Mandela, Clinton flew to Johannesburg to address a gathering of American and South African business leaders, including representatives of top companies such as Boeing, Chevron, EMD/Caterpillar, FedEx Express, GE and Walmart.
Enormous growth
"Looking across Africa, we see enormous economic growth even as the global economy continues to struggle. Seven of the world's 10 fastest-growing economies are in this region," Clinton said.
"These emerging markets present enormous opportunity for American trade and investment."
South Africa is the largest US trade partner in the region at $22-billion annual trade between them, she added.
On Tuesday the US Export Import Bank is set to sign a $2-billion deal to support South Africa's ambitious plans for renewable energy, a key component of the country's drive to double its electricity supply.
Clinton is set to leave South Africa on Thursday for Nigeria and then Benin. She is also expected in Ghana for the state funeral of late president John Atta Mills, before heading to Istanbul for talks on the crisis in Syria. – Sapa-AFP