President Obama has shaken hands with Cuban President Raul Castro, an unprecedented gesture of friendship which occurred fittingly at the memorial service for Nelson Mandela today.
The handshake between the leaders of the two Cold War enemies came during a ceremony that's focused on the former South African President's legacy of reconciliation.
Obama was greeting a line of world leaders and heads of state attending the memorial in Johannesburg.
He also shook hands with Brazilian President Dilma Rousseff, who has clashed with Obama over alleged National Security Agency spying.
The U.S. and Cuba have recently taken small steps toward rapprochement, raising hopes the two nations could be on the verge of a breakthrough in relations.
But skeptics caution that the two countries have shown signs of a thaw in the past, only to fall back into old recriminations.
Obama arrived an hour late to the memorial service on Tuesday after missing the opening speeches when his motorcade got stuck in traffic. The President was greeted with a rapturous ovation when he arrived at the FNB Stadium to pay tribute to the former South African leader.
Obama described Mr Mandela as the 'last great liberator of the 20th century' and compared him to Ghandi and Martin Luther King in a powerful address to the crowds.
Addressing the people of South Africa, he said: 'Thank you for sharing Nelson Mandela with us. His struggle was your struggle, his triumph your triumph.
President Obama is leading an American delegation of former presidents and their families including George W Bush, his wife Laura, Bill and Hillary Clinton and their daughter Chelsea and Jimmy Carter.
Obama, who greeted crowds who gathered in the torrential rain, said: 'He changed views but he also changed hearts. For the people of South Africa, for the people he inspired around the globe, his passing is rightly a time of mourning and a time to celebrate his life.
But I believe it should also be a period of self-reflection. With honesty, regardless of our station or circumstance, we must ask: how well have I applied his lessons in my own life? It's a question I ask myself as a man and as a President. We can't allow our progress to cloud the fact that our struggle is not done.
''We will never see the likes of Nelson Mandela again but let me say to young people in South Africa and around the world, you too can make his life work your own.
The U.S. President added: 'After this great liberator is laid to rest; when we have returned to our cities and villages, and rejoined our daily routines, let us search then for his strength - for his largeness of spirit - somewhere inside ourselves.