In a sometimes awkward public appearance in which Castro fiddled with his headphones and complained about translation problems, the Cuban president unexpectedly fielded questions from US reporters.
"Give me a list of the political prisoners and I will release them immediately," Castro said when challenged about the Communist island's human rights record.
"After this meeting is over, you can give me a list of political prisoners. And if we have those political prisoners, they will all released before the night ends," he said.
Obama's visit to Cuba, the first by a US president in 88 years, has raised hopes among struggling Cubans that decades of economic and political stasis may be coming to an end.
But the detention of dozens of pro-democracy protesters yesterday and the deployment of a horde of secret police around Old Havana have served as a stark reminder of the regime's iron grip on power.
