JOHANNESBURG, South Africa -- President Barack Obama and Cuban leader Raul Castro shook hands and exchanged greetings Tuesday in a surprise encounter at the memorial service for former South African President Nelson Mandela.
The brief meeting between the two men representing countries that have been at odds for more than a half-century came as Obama mounted the podium to take his seat on the dais. Castro, who arrived at the stadium earlier in the day, was the first head of state to greet Obama as he walked to his seat. The White House has said the handshake was not planned.
The encounter, however, did not appear to influence Obamas speech. He criticized countries although not naming Cuba where the will of the people is not being respected.
"Our work is not done," Obama said. "Around the world today, men and women are still imprisoned for their political beliefs; and are still persecuted for what they look like, or how they worship, or who they love."
In Cuba on Tuesday, more than a dozen human rights activists were arrested during protests to mark International Human Rights Day.
Obama received the largest cheer of all foreign visitors when he took the stand Tuesday at a FNB Stadium in Soweto, where Mandela made his last public appearance. He died Thursday at the age of 95, and will be buried on Sunday.
The audience included more than 90 world leaders, most from democracies but also countries like China, Cuba, Vietnam and Zimbabwe where citizens continue to be jailed for dissent.
And in his speech, Castro said he was ready to negotiate "with those who think differently."
Castro was not the only leader at odds with the U.S. who spoke during the memorial service. Brazilian President Dilma Rousseff, who canceled a state visit to the U.S. this year over allegations of U.S. spying, greeted Obama warmly after he shook hands with Castro.
Mandela was one of a kind, Rousseff told tens of thousands of people at the stadium.
We must pay homage to this unmatched example of humanism, Rousseff said.
She described some of his characteristics as his stoic form and patience, enlightened determination and strength.
She said Brazilian people felt close ties to South Africa.
Like the South Africans who mourn with their chants, we the Brazilian nation proudly carry African blood in our veins and we too mourn.
The Brazilian government and people bow down to the memory of Nelson Mandela, said Rousseff, who was accompanied at the funeral by several former Brazilian presidents.
It was never going to be easy for South Africa to host such an array of guests.
Within the small VIP area were Palestinian President Mahmoud Abbas, Yuli-Yoel Edelstein, speaker of the Israeli Knesset and Iranian leader Hassan Rouhan. Regional strongman Robert Mugabe of Zimbabwe was seated not far from the prime ministers of Canada, Australia and Britain who have banned him from entering their countries, citing human rights and stolen elections.
More than 20 of the governments represented stand accused by Amnesty International of holding prisoners, jailed for political rather than criminal acts.
Mr. Mandela received a life sentence for treason in 1963 and was only released in 1990 ahead of multiparty election won by his party, the African National Congress (ANC).
Crowds from across Johannesburg had queued all night to enter the arena in the black suburb of Soweto where the final game of the soccer world cup took place in 2010.
But rain that began early Tuesday reduced the attendance and more than a quarter of the 80,000-seat stadium was empty.
The late presidents family was led by his two surviving widows, Graça Machel and Winnie Madikizela whom Mandela divorced in 1996. Another ex-wife, Evelyn Masse, died in 2005.
The last speaker at Tuesdays service was South African President Jacob Zuma who thanked the world leaders and the people of South Africa for giving such a send-off to his late friend and colleague.
As President Obama and other visitors return home, critics and the media in South Africa are likely to step up comparisons between Mr. Zuma and the man he will spend much of this week laying to rest.