奥巴马前往南非

U.S. President Barack Obama is on his way to South Africa, continuing a three-nation African tour aimed at expanding U.S. engagement on the continent.

Mr. Obama departed Senegal Friday, after a two-day visit where he met with President Macky Sall and promoted democracy and rule of law.  The president also made an emotional visit to Goree Island, a symbol of the 18th century slave trade.

It is not clear whether the South African leg of Mr. Obama's trip will include a visit with anti-apartheid legend Nelson Mandela, who is critically ill in a Pretoria hospital.  White House officials said Thursday any such visit would be up to the Mandela family.

On Saturday, President Obama plans to visit Robben Island, the prison where Mr. Mandela spent much of his 27 years behind bars.

President Obama paid tribute to the ailing former South African leader Thursday, calling him a "hero for the world."