Arriving on stage at FNB stadium in Johannesburg to pay tribute to Nelson Mandela, President Barack Obama shook hands with dozens of other world leaders, pausing briefly to grasp the hand of Cuban President Raul Castro.
The greeting quickly sparked a strong debate on Twitter between those who praised and disagreed with the handshake, given that the United States does not share diplomatic relations with Cuba.
Former U.S. President Jimmy Carter tells Becky that the gesture is "significant."
