The government of Cuba has told the United Nations special rapporteur on torture that he can't visit the island, reversing an invitation issued to him in February last year.
The visit by Manfred Nowak was to have the been the first by an independent UN expert to specifically monitor torture and other cruel treatment.
However, Mr Nowak said in a statement on Wednesday that Havana had told him it could not receive him before his mandate runs out at the end of October this year.
The BBC reports Cuban authorities have never allowed outside inspections of their prisons.
Cuba says it has no political prisoners and jails only criminals.