“We continue to ask the Cuban government to grant Alan Gross’s request to travel to the United States to visit his 90-year-old mother, Evelyn Gross, who is gravely ill. This is a humanitarian issue,” Toner added.

The head of the Cuban diplomatic mission in Washington, meanwhile, wrote to those who have expressed concerns about Gross’ health, saying he does not have cancer and suffers only “from chronic illnesses that are typical of his age, which are receiving adequate treatment.”

“Mr. Gross maintains a systematic physical exercise regime on a voluntary basis and eats a balanced diet that includes foods of his choice, which has allowed him to get rid of his former obese condition,” wrote José Ramón Cabañas.

“The Cuban government is sensitive to the humanitarian concerns” in the Gross case, he added, “and has expressed to [Washington] its willingness to find a reciprocal humanitarian solution that would also take into account highly sensitive humanitarian concerns of utmost importance for Cuba and its people” – the five spies.

Peter Kornbluh, a Cuba specialist at the National Security Archives, an independent research center in Washington, reported that he met with Gross in Havana last week and found him “extremely thin” and dispirited.

“He’s angry, he’s frustrated, he’s dejected — and he wants his own government to step up” and negotiate, Kornbluh told NBC News. “His message is that the United States and Cuba have to sit down and have a dialogue without preconditions. … He told me that the first meeting should result in a non-belligerency pact being signed between the United States and Cuba.”