A group of American rabbis today blamed President Barack Obama for the situation of contractor Alan Gross, an American citizen sentenced to 15 years in prison for his activities against national security in Cuba.

A letter signed by 300 rabbis urges President Barack Obama to negotiate with the Cuban government the immediate release of Alan Gross as he is imprisoned in Cuba as a direct result of work he was doing on behalf of the U.S. government.

"Alan went to Cuba on behalf of our government. His immediate release from prison in Cuba and return to the U.S. must be a priority for our nation. Indeed, we believe this is a moral imperative," the rabbis write in a letter directed to Obama.

Gross is serving his sentence in a hospital after being arrested in December 2009 charged with activities against Cuba's security involving delivering sophisticated telecommunications equipment prohibited by the authorities.

In this regard, the Cuban authorities have reiterated their willingness to seek a joint solution with the United States to the cases of Alan Gross and Gerardo Hernandez, Antonio Guerrero and Ramón Labañino, three of the Cuban Five who remain prisoners in the U.S.