US President Barack Obama and Cuba's Raul Castro greeted each other and shook hands at the Summit of the Americas, marking a new milestone in their diplomatic thaw.
A White House official characterized the meeting as an "informal interaction," adding that "there was not a substantive conversation between the two leaders."
Earlier Obama and Castro, separated by the presidents of Ecuador and El Salvador, stood in the second of three rows at a Panama City convention center as the country's national anthem was sung at the opening ceremony for the summit.
The sight of Obama and Castro in the same room instantly became a potent symbol of their bid to renew diplomatic ties that were severed in 1961. It was the first time that a Cuban leader attended the summit in its 21-year history.
Both smiling broadly, Obama and Castro had arrived separately for the two-day summit's inauguration.