US President Barack Obama (L) shakes hands with Cuban President Raul Castro in this still image taken from video courtesy of the South Africa Broadcasting Corporation (SABC) at the First National Bank (FNB) Stadium, also known as Soccer City, during late former South African president Nelson Mandela's national memorial service in Johannesburg Dec10, 2013. Obama shook hands with Cuba's Raul Castro at the memorial on Tuesday, a rare gesture between the leaders of two ideological opponents that reflected the anti-apartheid hero's spirit of reconciliation. [Photo/Agencies]

HAVANA - Cuba is upbeat about the handshake between US President Barack Obama and the island nation's leader Raul Castro in South Africa, indicating it was a possible sign of improving relations.

The Cuban government on Wednesday posted a photograph of the handshake, taken at the memorial service for late South African President Nelson Mandela, on its official website.

The picture was captioned "Obama greets Raul: could this ... be the beginning of the end of US aggression against Cuba?"

It was the first time Obama and Castro greeted each other in public, as both had previously avoided any potentially awkward encounters at international events.

Formal relations between the two countries were broken off in 1961.

The leaders met on Tuesday as Obama was making his way to the podium to speak at the service, which was held in Johannesburg's Soccer City Stadium in South Africa, and the White House later said the greeting was unplanned.

In 2000, then Cuban leader Fidel Castro exchanged polite greetings with the then US President Bill Clinton at a UN luncheon.