(CNN) -- The U.S. State Department called on Cuba on Monday to release an American who is serving a 15-year sentence on the island.
The renewed call came as Alan Gross begins his fourth year of imprisonment. He was arrested on December 3, 2009, for bringing in banned communications equipment as part of a State Department program to spread democracy.
Gross, 63, had argued that he was working to connect Cuba's small Jewish community to the Internet, but Cuban authorities said he had imported sensitive communications equipment to connect dissidents.
"The Cuban government should release Alan Gross and return him to his family, where he belongs," the State Department said in a written statement.
It praised Gross as a "husband, father, and dedicated professional with a long history of providing assistance and support to underserved communities in more than 50 countries."
Gross and his wife, Judy, are suing the U.S. government and the group for which he worked, citing what they call an "abject failure to advise, train and protect him."
The Grosses claim that both the U.S. government and the contractor, Development Alternatives Inc., based in Bethesda, Maryland, "failed to disclose adequately to Mr. Gross, both before and after he began traveling to Cuba, the material risks that he faced due to his participation in the project."
The suit also charges that the State Department and DAI failed to provide him with education and training that were necessary to minimize the risk of harm and should have delayed the project "until the risks subsided."
Instead, the couple allege, the company wanted to complete the project quickly "under part of a broader and very lucrative contract with the U.S. government."
Gross is battling chronic arthritis pain and has lost more than 100 pounds since his arrest, according to his lawyers, family and the State Department.
The Cuban government has disputed reports that his health is failing.
CNN's Jill Dougherty contributed to this report.