It is the handshake felt around the world or, at least, in the US and Cuba, two neighbouring countries better known for their enmity than cordiality.

Which is probably why the meeting of US President Barack Obama and his Cuban counterpart, Raul Castro, at the memorial service for Nelson Mandela, has fuelled talk of a possible rapprochement between the leaders of the two Cold War foes.

Afterall, it is only the second time in 60 years that a US president has shaken the hands of a Cuban Communist leader. President Clinton did it in 2000 during a United Nations summit in New York, when he shook hands with Mr Castro’s brother, Fidel. When news of that handshake leaked out, the White House denied it at first.

This time though, there is photographic evidence, clearly showing Obama and Raul Castro shaking hands. It prompted optimism in some quarters and outright hostility in others.

The Cuban government said the gesture may show the “beginning of the end of the US aggressions”.

But the BBC reported that Republicans on Capitol Hill were quick to condemn the gesture, with one Republican congresswoman chiding the move during an unrelated hearing on Tuesday.

“Sometimes a handshake is just a handshake, 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,” Florida Congresswoman Ileana Ros-Lehtinen, who is known for her opposition to the Castro government, told Secretary of State John Kerry.

The brief encounter between the American and Cuban presidents came during a ceremony in Johannesburg on Tuesday that celebrated former South African president Mandela’s legacy of reconciliation. Obama was greeting a line of world leaders before delivering a eulogy in which he urged a new generation to embrace Mandela’s life work as their own.

More than half a century after the US cut off diplomatic relations with Cuba, such exchanges between American and Cuban leaders are exceedingly rare. US officials have gone to great lengths to avoid having presidents meet Cuban leaders, even in passing.

Despite Tuesday’s handshake, Obama still offered an implicit criticism of governments like Cuba’s when moments later he said too many people embraced Mandela’s legacy of racial reconciliation but passionately resisted economic and other reforms.

“There are too many who claim solidarity with Madiba’s struggle for freedom but do not tolerate dissent from their own people,” Obama said, referring to Mandela by his clan name.

Obama also greeted Brazilian President Dilma Rousseff with a kiss on the cheek. Rousseff and Obama have clashed over reports the National Security Agency monitored her communications, leading the Brazilian leader to shelve a state trip to the US this year.

It remains to be seen whether history will treat the Obama-Castro moment at Mandela’s memorial service as it has these never-to-be-forgotten exchanges:

Mandela and South African president, Frederik de Klerk, shook hands on their shared Nobel Prize in 1993, while China’s Mao and the US’s Nixon made history in 1972.

Gorbachev and Reagan’s ’88 summit began with a handshake, while Egypt’s Sadat, Israel’s Begin and the US’s Carter sealed their ’79 peace deal with a show of hands

Richard Nixon welcomed Elvis Presley to the White House in ’70, while Brit Roger Bannister (centre) accepted the plaudits of rivals after breaking the four-minute mile in ’54

Princess Diana melted hearts greeting an ‘untouchable’ during an Indian visit in ’92. British PM Neville Chamberlain broke plenty with this exchange with Hitler in ’38