Obama says US has ‘moral imperative’ to help feed Africa

President Barack Obama, wrapping up the first leg of an African tour this morning, said Washington had a "moral imperative" to help the world's poorest continent feed itself and he then left for South Africa hoping to see ailing Nelson Mandela.

White House officials hope Obama's three-nation tour of Africa - his first substantial visit to the continent since taking office in 2009 - will compensate for what some view as years of neglect by America's first black president.

Before departing Senegal after a two-day stay, Mr Obama met farmers and local entrepreneurs to discuss new technologies helping to raise agricultural output in West Africa, one of the world's most under-developed and drought-prone regions.

Standing in front of the agricultural displays at an event hosted by Feed the Future, the US government’s global hunger initiative, Mr Obama said his administration was making food security a top priority of its development agenda.

“This is a moral imperative. I believe that Africa is rising and wants to partner with us: not be dependent but be self sufficient,” he said. “Far too many Africans endure the daily injustice of poverty and chronic hunger.

The health of Mandela, the 94-year-old former South African president and anti-apartheid hero clinging to life in a Pretoria hospital, dominated Mr Obama’s day even before he arrived in Johannesburg.

Asked on Thursday whether Mr Obama would be able to pay Mr Mandela a visit, the White House said that was up to the family.

"We are going to completely defer to the wishes of the Mandela family and work with the South African government as relates to our visit," deputy national security adviser Ben Rhodes told reporters in Senegal.

Members of Mr Mandela’s family as well as South African Cabinet ministers have visited the hospital where Mr Mandela is being cared for.

One of Mr Mandela’s daughters, Makaziwe Mandela, was among family members who arrived at the Pretoria hospital today. The ministers of health and defence also visited.

The anti-apartheid leader was taken to the hospital on June 8 to be treated for what the government said was a recurring lung infection. South Africans have held prayers nationwide, and many have left flowers and messages of support outside the hospital as well as his home in Johannesburg.

Yesterday, the office of South African President Jacob Zuma said Mr Mandela's health had improved overnight, and that his condition was critical but stable.

Mr Obama sees Mr Mandela, also known as Madiba, as a hero. Whether they are able to meet or not, officials said his trip would serve largely as a tribute to the anti-apartheid leader.

“I’ve had the privilege of meeting Madiba and speaking to him. And he’s a personal hero, but I don’t think I’m unique in that regard,” said Mr Obama. “If and when he passes from this place, one thing I think we’ll all know is that his legacy is one that will linger on throughout the ages.”

Like Mr Mandela, Mr Obama has received the Nobel Peace Prize and both men were the first black presidents of their nations.