Barack Obama has led tributes to Nelson Mandela urging the world to use the celebration of his life as a period of "self-reflection."
The US president spoke of the "heroic" life of the South African anti-apartheid hero describing him as the "last great liberator of the 20th century" as he addressed thousands gathered for the memorial service to Mr Mandela in the FNB Stadium in Soweto.
Mr Obama compared Mr Mandela's actions to those of Gandhi, Abraham Lincoln and US civil rights leader Martin Luther King but also warned against viewing Mr Mandela as detached from normal life.
"He was not a bust made of marble, he was a man made of flesh and blood," Mr Obama told the crowds in the stadium including leaders from more than 90 countries gathered at the stadium.
Mr Obama further singled out world leaders who have publicly welcomed gains made by Mr Mandela but resist reforms to tackle inequality and injustice.
"Around the world today we still see children suffering from hunger and disease and we still still see run down schools and we see young people without prospects for the future," he said.
"Around the world today men and women are still imprisoned for their political beliefs and are still persecuted for what they look like and how they worship and who they are, that is happening today.
"There are too many people who happily embrace Madiba's (Mandela's) legacy of racial reconciliation but passionately resist even modest reforms that would challenge chronic poverty and growing inequality.
"There are too many leaders who claim solidarity with Madiba's struggle for freedom but do not tolerate dissent from their own people.
"There are too many of us on the sidelines comfortable in complacency or cynicism."
Mr Obama warned against viewing Mr Mandela as "detached" from normal life.
"It was precisely because he could admit to imperfection, because he was so full of good humour, even mischief despite the heavy burdens that he carried, that we loved him so," he said.
"He was not a bust made of marble, he was a man of flesh and blood, a son and a husband, a father and a friend, that is why we have learned so much from him and that is why we can learn from him still.
"Nothing he achieved was inevitable, in the arc of his life, we see a man who earned his place in history through struggle and shrewdness and persistence and faith."
Mr Obama's speech came after he shook hands with Cuban president Raul Castro among other world leaders gathered at the service. The US president was cheered by the assembled crowds. Boos were heard for the current South African president Jacob Zuma.
Those attending included Prime Minister David Cameron and his three surviving predecessors, Sir John Major, Tony Blair and Gordon Brown.
Also seen arriving at the service were supermodel Naomi Campbell, rock star Bono, former South African president FW De Klerk, former US president Bill Clinton and his wife ex-US secretary of state Hillary Clinton, former French president Nicolas Sarkozy and the current French president Francois Hollande.
Mr Mandela, who died last Thursday aged 95, made his last public appearance at the stadium at the closing ceremony of the 2010 football World Cup.