Pope Benedict XVI criticised the 50-year-old US trade embargo on Cuba as he wrapped up a three-day visit to the island on Wednesday, urging reconciliation and greater freedoms.

The leader of the world’s 1.2 billion Catholics also met with Cuba’s revolutionary icon and former president, Fidel Castro.

"May no one feel excluded ... from taking up this exciting search for his or her basic freedoms, or excused from this by indolence or lack of material resources, a situation which is worsened when restrictive economic measures, imposed from outside the country, unfairly burden its people," the pontiff said.

The pope also led a public Mass in Havana's vast Revolution Square where Castro, 85, once drew huge crowds to listen to his fiery speeches.

Surrounded by 10-storey high images of Castro's late comrades Ernesto "Che" Guevara and Camilo Cienfuegos, the pope read a sermon that continued the main themes of his trip - that Cuba must build a more open, less controlled society, with a bigger role for the church as a buffer against "trauma" or social upheaval.

The Vatican estimated that 300,000 people were in the crowd.

Benedict's visit comes as Cuban President Raul Castro has undertaken economic reforms to encourage more private enterprise and embraced the church as an interlocutor on social issues.

But while the pope is urging Cuba to make deeper changes, the government sees its reforms as a way of strengthening communist rule, not weakening it.

After the Mass, Castro, the former president, visited Benedict at the Vatican embassy where the two world leaders with widely divergent political views chatted for 30 minutes in what a Vatican spokesman called a "very cordial" atmosphere.

The friendly meeting contrasted with the beginning of Benedict's visit when he sharply criticised the communist system that Castro put in place after taking power in a 1959 revolution.

On the flight to Mexico beginning his Latin American trip on Friday, the pope said communism had failed in Cuba and that the country needed a new economic model.

Marino Murillo, a vice president in the council of ministers and the country's economic reforms czar, made it clear that change to Cuba's one-party political system was not on the agenda.

"In Cuba there won't be political reform," he said at a news conference. "We are talking about the update of the Cuban economic model to make our socialism sustainable."