President Barack Obama has shaken hands with Cuban President Raul Castro at a memorial service for former South African President Nelson Mandela.

The handshake between the leaders of the two Cold War enemies came during a ceremony that's focused on Mandela's legacy of reconciliation. Obama was greeting a line of world leaders and heads of state attending the memorial in Johannesburg. Among those he greeted was 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.