Obama pledges to help Africa, pays tribute to Mandela

Protesters pray infront of the U.S. embassy during a protest against the visit of U.S. President Barack Obama in PretoriaBy Mark Felsenthal and Jeff Mason ABOARD AIR FORCE ONE (Reuters) – U.S. President Barack Obama paid tribute to anti-apartheid hero Nelson Mandela as he flew to South Africa on Friday but played down expectations of a meeting with the ailing black leader during an Africa tour promoting democracy and food security. 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. …