"He is a personal hero. I think he is a hero for the world, and if and when he passes from this place, one thing I think we all know is that his legacy is one that will linger on throughout the ages," Obama said in Senegal.
Mandela was today on life support in a Pretoria hospital and his condition was casting doubt over Obama's visit to South Africa, due to begin tomorrow.
Obama, using Mandela's clan name "Madiba", said Mandela had given him a "sense of what is possible in the world, when righteous people of goodwill work together".
