(JTA) — Alan Gross, a Jewish-American contractor in prison in Cuba, asked President Obama in a letter to help secure his release.

The letter was sent on Tuesday, the fourth anniversary of Gross’ imprisonment.

“It is clear to me, Mr. President, that only with your personal involvement can my release be secured. I know that your administration and prior administrations have taken extraordinary steps to obtain the release of other U.S. citizens imprisoned abroad – even citizens who were not arrested for their work on behalf of their country,” the letter, published by the Washington Post, read.

Gross, a subcontractor for the State Department on a mission to hook up Cuba’s small Jewish community to the internet, was arrested in December 2009 as he was leaving Cuba. He is serving a 15-year sentence for “crimes against the state.

“I have worked in community development for nearly 30 years. I have carried out missions on behalf of my country with pride, even in the face of risks to my safety. I did so because I believed in my country, in my government. I still want to believe that my government values my life and my service, and that a U.S. passport means something,” Gross’ letter read.

The letter was sent a day before a scheduled demonstration by Jewish and faith groups, and Gross’ wife, Judy, at Lafayette Park outside the White House along with officials from the Jewish Community Relations Council of Greater Washington.

The U.S. State Department on Monday called on the Cuban government to release Alan Gross “immediately and unconditionally.”

“It is gravely disappointing, especially in light of its professed goal of providing Cubans with internet access, that the Cuban government has not allowed Mr. Gross to return to his family, where he belongs. Mr. Gross is a 64-year-old husband, father, and dedicated professional with a long history of providing aid to underserved communities in more than 50 countries,” the State Department’s statement read.

The Cuban government has indicated that it wants the United States to allow the return of Cuba five spies currently in prison or on probation in the United States.