Argentine President Cristina Fernandez is attending the VII Summit of the Americas in Panama City where she is expected on Saturday to strongly criticize the United Kingdom over the 'militarization' of the Falklands/Malvinas and revelations of massive espionage of Argentina by London.
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.
A US official characterized the Obama-Castro greeting as an informal interaction, adding that there was not a substantive conversation between the two leaders.
A widely anticipated broader conversation -- the first between US and Cuban leaders since ties broke in 1961 -- is expected on Saturday. The two leaders briefly shook hands once before, at Nelson Mandela's memorial service in Johannesburg in 2013.
This summit in Panama has such a special dimension, Organization of American States secretary general Jose Miguel Insulza told the gathering, noting it was the first time all 35 nations were represented.
Ban added: The presence here today of President Raul Castro of Cuba embodies a longing expressed by many in the region.
Senior Obama aide Ben Rhodes said the extent of Saturday's Obama-Castro meeting had yet to be decided, but that they will take stock of the negotiations to reopen embassies and discuss lingering differences.
Rhodes said Obama and Castro had already discussed the ongoing negotiations and the summit by telephone Wednesday -- their second phone call since December, when they announced that the United States and Cuba would move to normalize relations.
But in a move that could irritate Havana, Obama held a closed-door discussion before the summit with dissident lawyer Laritza Diversent and political activist Manuel Cuesta Moura, along with a dozen other activists from the Americas.
While declaring that the days of US meddling in the region were over, Obama promised civil society representatives that the United States will stand up alongside you every step of the way.
Turning to Cuba, Obama said that even as a new chapter in relations was launched, we'll have our differences, government to government, with Cuba on many issues.
Cuban government supporters confronted dissidents on the sidelines of the summit.
For his part, Castro held talks with the president of the US chamber of commerce, Tom Donohue, putting together the leader of the only communist regime in the Americas with a major figure of capitalism.