Obama today left for South Africa with his wife,
Michelle, on board Air Force. Former President George W Bush was also on the plane, along with former first ladies Laura Bush and Hillary Clinton.
The occasion was a rare one, with four American Presidents getting together in Johannesburg.
Former President Bill Clinton will be reaching South Africa from Rio de Janeiro and former President Jimmy Carter also planned to join the group here.
Palestinian leader Mahmud Abbas, Sri Lanka President Mahinda Rajapaksa, Bangladesh President Abdul Hamid and UN Secretary General Ban Ki-moon will also attend the event.
Britain's Prince Charles will represent Queen Elizabeth II at the memorial service.
At least 91 heads of state have already confirmed their attendance and more were believed to be coming, officials said.
“The world literally is coming to South Africa,” Clayson Monyela, spokesman for the Department of International Relations and Cooperation, said adding that the large number of high profile guests arriving was unprecedented.
“I don't think it has ever happened before. We will have all organisations of the world. For example, the United Nations will be represented by the Secretary General Ban Ki-Moon, the African Union by Commission Chairperson Nkosazana Dlamini Zuma, and we have princes and princesses, Kings and Queens coming,” he said.
