The United States said Saturday it was "deeply disappointed' by President Raul Castro's decision to keep US contractor Alan Gross behind bars while announcing the release of nearly 3,000 prisoners. "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," State Department acting spokesman Mark Toner said in a statement.