The Obama-Castro meeting was the climax of their surprise announcement on December 17 that, after 18 months of secret negotiations, they would seek to normalize relations between their two nations.
  
"This is obviously a historic meeting," said Obama, who spoke first after they sat down in polished, wooden chairs for their talks in a blue-carpeted room on the sidelines of the 35-nation Summit of the Americas.
  
Obama declared that, after 50 years of U.S. policies that had not worked, "it was time for us to try something new."
  
"We are now in a position to move on a path toward the future," he said, adding that the immediate task was to reopen embassies that shuttered after the 1961 diplomatic break.
  
Castro cracked a smile when Obama acknowledged that the two sides will continue to have differences on human rights and other issues.
  
After Obama spoke, the two men stood up and shook hands.
  
Saying he agreed with everything Obama stated, Castro said the two government can still have differences but "with respect of the ideas of the others."
  
"We are willing to discuss everything but we need to be patient, very patient," he said.
  
"We already expressed to some American friends in other occasions that we are willing to talk about everything."
  
When Castro said he hoped the U.S. and Cuban delegations will listen to their presidents' instructions, Obama laughed.
  
The two leaders, who had spoken on the phone in December and again on Wednesday, shook hands again and reporters were ushered away for a closed-door discussion.
  
Obama told reporters later that the conversation was "candid and fruitful" and that he did not shy away from telling Castro that Washington would keep airing concerns about democracy and human rights.
  
Obama and Castro had already made conciliatory speeches moments earlier during the summit, sitting in an oval table with some 30 other regional leaders.
  
U.S.-Cuban tensions have vexed Washington's relations with the region for decades.
  
"This shift in U.S. policy represents a turning point for our entire region," Obama told the summit.
  
Addressing the leaders next, Castro declared: "President Obama is an honest man."
  
He was the first Cuban leader to attend the summit in its 21-year history.
  
Colombian President Juan Manuel Santos summed up the mood, saying "an old obstacle in relations between Latin America and North America is being removed."
  
But both leaders acknowledged that the two countries still have work to do restore ties.
  
Despite their differences, "there wasn't tension" during the bilateral meeting, a senior U.S. administration official said.
  
Obama and Castro discussed the embassy negotiations and instructed their teams to swiftly resolve lingering issues during their private talks, the official said.
  
"Our expectation is this could be concluded relatively quickly," the official said.
  
Castro mentioned his desire to see the end of the U.S. embargo, which forbids most trade and American tourism to the island. Obama has urged the U.S. Congress to end it.
  
Addressing a key Cuban demand, Obama told Castro that he would decide whether to recommend removing Cuba from a U.S. list of state sponsors of terrorism in the "coming days," the official said.
   
But as Obama sought to turn the page on Cold War-era tensions with Cuba, a spat with Venezuela also took the stage.
  
Venezuelan President Nicolas Maduro criticized Obama, but the U.S. leader had already left the room to head to a bilateral meeting with Colombian President Juan Manuel Santos.
  
"I respect you, but I don't trust you, President Obama," Maduro said.
  
He urged Obama to lift sanctions against Venezuelan officials accused of committing human rights abuses.
  
The order has particularly irritated Maduro because it calls Caracas a U.S. national security threat.
  
After Maduro complained that Obama had ignored his pleas to hold talks since the Venezuelan leader was elected in 2013, it emerged that the two briefly spoke on the sidelines of the summit.
  
Obama "reiterated that our interest is not in threatening Venezuela, but in supporting democracy, stability and prosperity in Venezuela and the region," said Katherine Vargas, a White House spokeswoman.
  
The White House sought to ease tensions ahead of the summit, saying it did not really believe that Venezuela posed a national security threat.
  
Maduro's leftist allies rallied behind him.
  
"Our people will never again accept tutelage, meddling and intervention," said Ecuador's President Rafael Correa. (AFP)