HAVANA (AP) - It was the briefest of moments, just seconds, two presidents shaking hands and exchanging pleasantries amid a gaggle of world leaders together to honor the late Nelson Mandela.
It would hardly have been noteworthy, except the men locking hands in Johannesburg were Barack Obama and Raul Castro, whose nations have been mired in Cold War antagonism for more than five decades.
A single, cordial gesture is unlikely to wash away bad blood dating back to the Eisenhower administration. But in a year that has seen both sides take small steps at improving the relationship, the handshake stoked talk of further rapprochement.
"On the one hand you shouldn't make too much of this. Relations between Cuba and the United States are not changing tomorrow because they shook hands," said Geoff Thale, a Cuba analyst at the Washington Office on Latin America, a U.S.-based think tank.
He contrasted the moment to a 2002 development summit where then-Mexican President Vicente Fox asked Fidel Castro to leave to avoid having him in the same room as U.S. President George W. Bush.
"What's really striking here is the contrast," Thale said. "It's a modestly hopeful sign, and it builds on the small steps that they're taking."
Not everyone was so happy about it.
"Sometimes a handshake is just a handshake," said Ileana Ros-Lehtinen, a Cuban-American congresswoman from Florida who until January 2013 was chair of the House Committee on Foreign Affairs. "But when the leader of the free world shakes the bloody hand of a ruthless dictator like Raul Castro, it becomes a propaganda coup for the tyrant."
Obama and Castro's encounter is the first of its kind between sitting U.S. and Cuban presidents since Bill Clinton and Fidel shook hands at the U.N. in 2000.
It came as Obama greeted a line of world leaders on his way to the podium for a speech at the memorial.
Obama also had a cheek-kiss for Brazilian President Dilma Rousseff. The two have clashed over reports the National Security Agency monitored her communications, leading the Brazilian leader to shelve a state trip to the U.S. earlier this year.
In another potentially uneasy exchange, Obama briefly greeted Afghan President Hamid Karzai, whose refusal to sign a security agreement with the U.S. before year's end has irritated the administration.
Obama adviser Ben Rhodes said the handshakes were not planned in advance and didn't involve any substantive discussion.
"The president didn't see this as a venue to do business," he told reporters traveling back to Washington aboard Air Force One.
The U.S. and Cuba have held multiple rounds of talks on restoring direct mail service and immigration issues, with more scheduled for January. Diplomats on both sides report cordial relations and call each other at home. The two nations' coast guards reportedly work well together on things like drug interdiction.
Cuban state television broadcast images of Tuesday's historic handshake, as well as a snippet of Obama's speech. It did not, however, include his implicit criticism of governments like Havana's: "There are too many who claim solidarity with (Mandela's) struggle for freedom but do not tolerate dissent from their own people," Obama said.