(JTA) — Forty members of the House of Representatives signed a letter warning Cuba that improved relations are contingent on the release of a jailed Jewish American.

Alan Gross, 60, has been held since Dec. 3; he was arrested while reportedly assisting the Cuban Jewish community to connect to the Internet. His congressman, U.S. Rep. Chris Van Hollen (D-Md.), initiated the letter.

“It is our understanding that at the time of his arrest, Mr. Gross was in Cuba to help the Jewish community improve their ability to communicate with Jews, both in Cuba and overseas,” said the letter sent Tuesday. “He was working pursuant to a U.S. government contract.” The Cuban government has banned such projects of the U.S. Agency for International Development.