The husband told the judge the couple acted not for money or because they were anti-American, but because of their beliefs.

"Our overriding objective was to help the Cuban people defend their revolution," he said.

The couple pleaded guilty last year after their June 2009 arrest.

Known as "Agent 202," Myers pleaded guilty last November to a three-count complaint charging him with conspiracy to commit espionage and two counts of wire fraud.

His wife, known as "Agent 123" and "Agent E-634", pleaded guilty to one count of conspiracy to gather and transmit national defence information.

They also agreed to forfeit $1.7m from the sale of their apartment and other goods.

'Country betrayed'

Myers said US-Cuban relations had long been marked by hostility and misunderstanding and that he sought to alleviate the fears of the Cuban people who felt threatened.

Reggie Walton, the district judge, said the couple had betrayed their country, showed no remorse and even seemed proud of what they had done.

The couple were recruited by Cuba during the 1970s.

Myers rose to senior analyst on European intelligence with "top secret" clearance and access to scores of classified documents, which he passed to the Cuban government

US prosecutor Michael Harvey said at Friday's hearing that the couple received medals from the Cuban government and flew to Cuba in 1995 for a private meeting with the country's leader, Fidel Castro.

"If you believed in the revolution," the judge told the couple as they stood before him in the packed courtroom, "you should have defected".

Myers, who left the State Department in 2007, is telephone inventor Alexander Graham Bell's great-grandson.