Fidel Castro has said his brother, Raul, introduced himself to US President Barack Obama in English at the funeral for former South African President Nelson Mandela, telling him, "Mr President, I am Castro".

In an interview about Mandela in Cuban state media on Thursday, Castro congratulated his brother, who took over as president of Cuba in 2008, for his "steadfastness and dignity, when, with a friendly but firm gesture, he greeted the head of the US government and told him in English, 'Mr President, I am Castro'".

Raul Castro and Obama shook hands at Mandela's funeral on December 10, setting off speculation about whether it signalled a warming of ties between the two nations after decades of animosity.

The US and Cuba downplayed the handshake, saying it was unplanned and went no further than pleasantries.

But the meeting had resonance because relations between the two countries have recently warmed.

Last month in Miami, Obama said that it may be time for the US to revise its policies towards Cuba, against which it has had a trade embargo for more than 50 years.

Obama questioned whether the policy that was put in place in 1961 remains an effective way of dealing with Washington's differences with the communist-ruled island nation.

Fidel Castro, 87, underwent an operation for intestinal bleeding in 2006 and never fully recovered. He handed over presidential powers to his younger brother, Raul, in 2008.