Cuba's Supreme Court has rejected an appeal from jailed U.S. contractor Alan Gross, who was sentenced to 15 years in prison in March for crimes against the communist state.

Cuban authorities arrested Gross in December 2009 for bringing communications equipment into the country.

Gross was working for a private firm that was contracted by the U.S. Agency for International Development. He was accused of distributing Internet equipment and satellite phones to Cuban dissident groups. Gross said he was trying to improve Internet access for the island's small Jewish community and his actions were not intended to be a threat against the Cuban government.

The U.S. government has called for his release. The White House has described the sentence as “another injustice.”

His family has appealed on humanitarian grounds for the 62-year-old contractor to be returned home.

The United States and Cuba do not have formal diplomatic relations, only interests sections that are technically part of the Swiss embassies in each other's capitals.