Cuban President Raul Castro has thanked Pope Francis for his role in brokering the rapprochement between Havana and Washington.

The first South American Pope played a key role in secret negotiations between the United States and Cuba that led to the surprise announcement in December that the two countries would seek to restore diplomatic ties after more than 50 years of tensions.

Pope Francis meets Cuban President Raul Castro during a private audience at the Vatican. Credit:Reuters

Mr Castro, who was accompanied by his Foreign Minister Bruno Rodriguez Parrilla, was holding a "strictly private" meeting with the pontiff in the Vatican.

The Holy See has said the Argentine pope personally mediated between the two sides, and the Vatican hosted delegations from the two countries in October.