Cuba`s lengthy imprisonment of an American contractor is a major obstacle to improving frosty ties between Havana and Washington, a senior US diplomat warned Tuesday.
Alan Gross, 65, Wednesday marks the fifth anniversary of his December 3, 2009 arrest in Cuba which saw him later sentenced to 15 years in prison in 2011.
He was convicted of "acts against the independence or territorial integrity of the state" for allegedly distributing communications equipment while working for the aid agency USAID.
"His release remains a top priority of the United States," deputy State Department spokeswoman Marie Harf told reporters.
"His continued incarceration represents a significant impediment to a more constructive bilateral relationship," she said, adding Washington renewed its "call for the Cuban government to release Alan Gross immediately."
Washington has long called on Havana to release Gross, and voiced growing concern about his health, amid reports he has lost about 100 pounds (45 kilos).
His family have also said that he is gradually losing hope of ever being freed.
Harf stressed that the US had used every "diplomatic channel to press for his release publicly and privately, and we will continue to do so."
Havana has suggested it could release Gross if Washington freed the remaining "Cuban Five" intelligence agents, who were convicted in a 1998 US spy case -- a prospect Washington has roundly rejected.
The United States and Cuba have not had full diplomatic relations since 1961. In 1962, Washington imposed an economic embargo on the island, the only Communist-run country in the Americas.