Clinton made the appeal after speaking with family members at the State Department a day before U.S. and Cuban officials are to meet in Washington for immigration talks. She said U.S. representatives at the those talks would raise the case of the contractor, Alan P. Gross, and tell them that his release would help improve U.S.-Cuban ties.
"We will underscore that the continued detention of Alan Gross is harming U.S.-Cuba relations," Clinton said in a statement released after she met with the contractor's wife, Judy Gross, and other family members.
Friday's immigrations talks are the latest in a series intended to monitor adherence to a 16-year-old agreement under which the United States issues 20,000 visas to Cubans a year, although in the past the sides have used the meetings to delve into more contentious issues.
Gross, a 60-year-old native of Potomac, Md., was working in Cuba for a firm contracted by the U.S. Agency for International Development when he was arrested as a suspected spy Dec. 3 at Havana's Jose Marti International Airport. He has been held without charge at the capital's high-security Villa Marista prison ever since.
"We are deeply concerned about his welfare and poor health, and we have used every available channel to push for his release," Clinton said. "As I told the family today, we will continue to do so."
Judy Gross has said that her husband is a veteran development worker who was helping members of Cuba's Jewish community use the Internet to stay in contact with each other and with similar groups abroad. She said her husband had brought communications equipment intended for humanitarian purposes, not for use by Cuba's small dissident community.
Satellite phones and other telecommunications materials are outlawed in Cuba, where the government maintains strict control over Internet access and the media.
Last month, the head of Cuba's high court said the communist island has yet to open a legal case against Gross. Formal charges cannot be filed in Cuba without a judicial accusation and the opening of a court case, so it appears unlikely charges against Gross are imminent.
It is rare for suspects to be held for extended periods in Cuba without charges or a case being opened. But Supreme Court President Ruben Remigio said in late May that "there still is not a case related to this matter," and he did not know whether prosecutors were working on one.