"Five years ago today Alan Gross was arrested for his efforts to help ordinary Cuban citizens have greater access to information through the Internet," White House press secretary Josh Earnest said in a statement.
President Barack Obama's administration "remains focused on securing Alan's freedom from a Cuban prison" and officials in Washington are "deeply concerned" about the health of the 65-year-old Gross, Earnest said.
"The Cuban Government's release of Alan on humanitarian grounds would remove an impediment to more constructive relations between the United States and Cuba," the statement concluded.
Gross was arrested in Havana in December 2009 with satellite communications equipment he was planning to distribute among Cuba's Jewish community.
He traveled to the island for Development Alternatives Inc., a Maryland company acting under a contract with the U.S. Agency for International Development to expand Internet access and the flow of information in Cuba.
Cuban authorities said Gross was illegally aiding dissidents and inciting subversion. He was eventually convicted and sentenced to 15 years.
"It is gravely disappointing" that Gross faces "a sixth year of unjustified imprisonment in difficult conditions in Cuba," the State Department said Tuesday.
Gross' health has deteriorated during his captivity and he has developed degenerative arthritis in one leg, his family says.
"After five years of literally wasting away, Alan is done," his wife, Judy Gross, said Wednesday in a statement. "It is time for President Obama to bring Alan back to the United States now; otherwise it will be too late."
Last month, a federal appellate court in Washington rejected Alan Gross' lawsuit against USAID for allegedly failing to alert him to the risks that his work in Cuba entailed.
The U.S. Court of Appeals for the District of Columbia on Friday upheld a lower court's finding that the government has sovereign immunity because the damage the plaintiff suffered occurred outside the United States.
In the meantime, US president Barack Obama has been urged by international lobbyists to free the three anti-terrorist Cubans who have been held in US federal prisons since 1998.
Known as the Cuban Five around the world, Rene Gonzalez, Fernando Gonzalez, Antonio Guerrero, Gerardo Hernandez and Ramon Labañino, were given unfair and extremely long prison terms by a Miami court in 2001 after they monitored Florida-based violent organizations that planned terrorist actions against Cuba. Fernando and Rene already returned to Cuba after having fully served their prison sentences, but Antonio, Gerardo and Ramón are still incarcerated.
Havana has suggested an exchange of Gross for three Cuban intelligence agents who have been behind bars in the United States since 1998.
The United States rejects talk of a prisoner swap, instead demanding that Cuba release Gross without conditions.