Cuba's high court Friday upheld a 15-year sentence imposed on US contractor Alan Gross, who has been in jail since his 2009 arrest on charges of espionage, triggering a swift outcry from Washington. The rejection of Gross's appeal was a blow to the recent gentle rapprochement between Cuba and the United States, and prompted US government officials to again demanded his immediate release. Gross, 62, was arrested in December 2009 for bringing satellite phones and equipment to Cuba's Jewish community while working as an independent contractor for a democracy-building program funded by the US Agency for International Development. In its ruling, the Supreme Court's chamber for crimes against the state issued a "final decision" rejecting his appeal, according to a statement posted on the Cubadebate (www.cubadebate.cu) official website. Gross's family were "heartbroken" by the decision and would petition President Raul Castro to "release Alan immediately on humanitarian grounds," his US lawyer, Peter Kahn, said. "While we are not surprised, we are extremely disappointed with today's ruling, which marks the end of Alan's legal process in Cuba," Kahn said in a statement. "The family is heartbroken by today's decision, but remains hopeful that there continues to be room for a diplomatic resolution of this matter." Only Cuba's Council of State, presided by Castro, can now order Gross to be freed. The lawyer also stressed that after 20 months in a Cuban prison "Alan and the entire Gross family have paid an enormous personal price in the long-standing political feud between Cuba and the United States," and urged both countries to resolve the dispute "diplomatically." Gross was sentenced to 15 years in prison on March 12 for "endangering the independence and security" of the Cuban state. During his appeals hearing in July, Gross "reiterated that he never had any intention of hurting the Cuban government or its people, and that he has always believed -- and still does so today -- in the sovereignty of the Cuban nation and its people," Kahn had said. The case drew the attention of former US president Jimmy Carter, who made a high-profile trip to Havana in March in a bid to secure Gross' release. The Nobel peace laureate met with the Castros and separately with Gross, but he was unable to win the American's freedom. Shortly after the Cuban ruling, Washington reacted angrily, calling once more for Gross to be released right away. "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," US National Security Council spokesman Tommy Vietor said in a statement. And acting State Department spokesman Mark Toner said "we deplore the ruling," calling Gross "a dedicated international development worker who has devoted his life to helping people in more than 50 countries." Gross "was in Cuba to help the Cuban people connect with the rest of the world," Toner added, calling for his immediate and unconditional release to "bring to an end the long ordeal that began well over a year ago." He vowed the United States would use "every available diplomatic channel" to free Gross. The contractor has lost some 40 kilograms (90 pounds) in jail, according to his wife Judy, while his daughter and mother-in-law are battling cancer, leading Gross's former employer to say he was "bitterly disappointed" by the verdict. "We urge that the Cuban government take into account the medical situation confronting Alan and his family, and quickly allow him to come home," said James Boomgard, president and chief executive of Development Alternatives, or DAI. For the past decade Havana has called on Washington to release five of its agents arrested in the United States in 1998 and later given heavy prison sentences for infiltrating anti-Castro circles in Florida.