Miguel Angel Moratinos arrived in Havana Tuesday just as one of the country's most high-profile political prisoners was said to be near death, the EUobserver reports.
Cuban activist Guillermo Farinas has been on a hunger strike for 132 days in defiance of his country's communist government.
Spain hopes Moratinos' visit will result in Cuba's release of political prisoners, starting with the 26 who are considered in poor health.
Moratinos told reporters before leaving for Havana he is hopeful his human rights mission will prompt Farinas to end his hunger strike.
The Spanish foreign ministry says a meeting between Moratinos and Cuba President Raul Castro "is not yet confirmed."