A bipartisan group of Unites States senators wrote a letter to Cuban President Raul Castro, urging him to release Alan Gross, a Jewish-American contractor who has been imprisoned in Cuba since December 2009.

The group of forty-four senators, led by led by Sens. Ben Cardin (D-MD) and Jerry Moran (R-KS), called Gross’ detention “a major obstacle” to improving relations between the two countries.

“Mr Gross’s ongoing detention in your country presents a major obstacle to any further actions to improve our bilateral relations,” the letter states.

The senators urge Cuba to release Gross, 63, on humanitarian grounds, saying he has lost 105 pounds since his arrest and suffers from degenerative arthritis and an untreated mass behind his shoulder.

Gross was sentenced to a 15-year term for bringing communications devices and Internet networks to the country’s Jewish community, causing Cuba to convict him of committing “crimes against the state.”

His wife, Judy said earlier this month that she feared for her husband’s life because his health has been continually deteriorating. Cuba rejected the plea, saying his condition is “normal” and that he is being held in a military hospital and not a prison.

“Alan’s family feels the Cuban government currently has no interest in negotiating his release,” said Jared Genser, the family’s attorney.

“Therefore, if the Cuban government wants to continue to detain him, it needs to understand that we are going to do everything necessary to shine a bright light on his failing health, their refusal to let him see his dying mother, and the injustice of his detention,” he said.

Sen. Moran issued a press release saying, “After three years of unjustly imprisoning American citizen Alan Gross, my colleagues and I are hopeful that the Cuban government will take action and grant his release.”