A special U.N. rights envoy has expressed concern over the number of dissidents held in Cuban jails, but says that a U.S. economic embargo is hampering attempts to improve Cuba's respect for political rights.

Christine Chanet said in a report this week to the U.N. Human Rights Commission that tightened U.S. sanctions have made life more difficult for Cubans in general and political opponents to President Fidel Castro in particular.

She said her main concern was still the detention of dozens of dissidents whose arrest while working as journalists, writers and members of associations in 2003 caused an international uproar.

Chanet has never been allowed to visit since Cuba since she became the U.N. commission's expert on the island three years ago.

Some information for this report was provided by AP and Reuters.