The U.S. State Department said on Saturday it deplored Cuba's failure to free Alan Gross - a U.S. citizen serving a 15-year prison term in a case that has stalled progress in U.S.-Cuba relations - as part of an announced humanitarian release of some 2,900 prisoners.

If this is correct, we are deeply disappointed and deplore the fact that the Cuban government has decided not to take this opportunity to extend this humanitarian release to Mr. Gross this holiday season, especially in light of his deteriorating health, and to put an end to the Gross family's long plight, Mark Toner, a State Department spokesman, said Saturday.

The Cuban government said on Friday it would free 2,900 prisoners in coming days for humanitarian reasons ahead of a visit next spring by Pope Benedict XVI.

Those to be pardoned do not include Gross, a government spokesman said in Havana. He was imprisoned after setting up Internet equipment as a subcontractor in a U.S.-funded program promoting political change in Cuba.

The Cuban government considered his work subversive. His arrest halted a brief warming in U.S.-Cuba relations that have been hostile since Fidel Castro embraced Soviet Communism after his 1959 revolution.

In a statement, Toner reiterated a U.S. call on Cuban authorities to release Gross and return him to his family, where he belongs. The State Department has said in the past that Gross was merely providing Internet access for Jewish groups in Cuba and should be released immediately.

(Reporting by Jim Wolf; additional reporting by Arshad Mohammed; Editing by Sandra Maler)