Cuba’s top court on Friday rejected the appeal of a Maryland man sentenced to 15 years in prison for his role in a secretive U.S. democracy project, dampening hopes of a resolution to a case that has further soured relations between the Cold War foes.

Alan P. Gross of Potomac has been held since December 2009 for distributing satellite communications equipment to Cuba’s Jewish community. He was sentenced in March for his activities, which Cuban authorities claimed were aimed at undermining the island’s Communist government.

The verdict disappointed the Obama administration and Gross’s family, who had hoped the court might reduce his sentence.

“We call on the government of Cuba to release Alan Gross immediately and unconditionally, to allow him to return to his family and bring to an end the long ordeal that began well over a year ago,” said Tommy Vietor, the National Security Council spokesman.

Gross’s attorneys had petitioned Cuba’s Supreme Court to reduce or dismiss the sentence. But the court denied Gross’s appeal in a “definitive resolution,” according to the state-run Web site Cubadebate.
Peter J. Kahn, an attorney for Gross, said in a statement that his family “is heartbroken by today’s decision, but remains hopeful that there continues to be room for a diplomatic resolution of this matter.”

At the time of his arrest, Gross was working for a Bethesda firm, Development Alternatives, which had won a $6 million contract from the U.S. Agency for International Development to promote democracy in Cuba. His work included the distribution of satellite phone equipment and computer gear. He lacked a permit, which is required under Cuban law and probably would have been denied.

U.S. officials have defended the program, saying it was aimed at helping Cubans break their government’s “information blockade.” Critics in Congress have said pro-democracy programs in Cuba are of questionable effectiveness. Democratic senators had held up disbursement of $20 million in pro-democracy funds for fiscal 2010 until this week because of their concerns.

Gross’s family has called for his release on humanitarian grounds. After 21 months in prison, the 62-year-old has lost about 100 pounds from his original 250; his mother-in-law and daughter are battling cancer.

Some analysts think the Cuban government is trying to push the Obama administration to drop its pro-democracy programs, which are illegal under Cuban law.