Headquarters for State Department in Washington (file photo)

The United States has arrested a former government official and his wife on charges of spying for Cuba.  The Justice Department says both suspects pleaded not guilty to the spying charges in a federal court in Washington on Friday. They are both being held until a detention hearing next Wednesday. The two are accused of passing top secret information to Havana over a 30-year period.

U.S. officials said they arrested Walter Kendall Myers and his wife Gwendolyn after an undercover operation in Washington. They said Walter Myers worked at the State Department for nearly 30 years, partly at the department's Bureau of Intelligence and Research, before retiring in 2007.

Authorities said an FBI agent, posing as a Cuban intelligence officer, contacted the Myers in April and asked them to obtain information for Havana. During a meeting, officials say the Myers agreed to provide information about U.S. officials working in Latin America, and they discussed their past activities on behalf of Cuba.

According to an affidavit,  Walter Myers told the FBI undercover agent that he was recruited after visiting Cuban officials in Havana in 1978, and later began passing information to intelligence agents, often in person. Myers said he was identified as "agent 202," and his wife was known as "agent 123."

U.S. officials did not comment on the kind of information the Myers are accused of passing to Cuba. They say employee records show Walter Myers accessed more than 200 sensitive reports about Cuba during his final year of work at the State Department.

Chris Simmons is a former U.S. counter-intelligence official involved with several recent Cuban spying cases in the United States. He says Havana is often seeking any kind of U.S. intelligence, not just about U.S. policy toward the island.

"The view from Havana is that U.S. classified information is a commodity to be bought, sold and traded to anyone that can come up with the right offer," said Simmons.

Simmons helped identify one of the highest-ranking Cuban spies in recent history, Ana Belen Montes who worked at the Defense Intelligence Agency. Montes pleaded guilty in 2002 and was sentenced to 25 years in prison.

The Myers are facing prison terms of up to 35 years if they are convicted of the charges against them, which include acting as illegal agents of a foreign government.

In an affidavit, U.S. officials said Gwendolyn Myers described her contacts with Cuban agents, such as passing secrets by exchanging shopping carts at the supermarket. Authorities say the couple also used short wave radio to take orders from Havana and to transmit information.

Simmons say Havana has long relied on short wave radio to send encoded messages using a system that converts letters into numbers.

"So anybody with a [short wave] receiver can hear it, but unless you have the encryption packet all you hear are the numbers. Uno, zero, cinco, cinco," he said.

Simmons says Cuba's intelligence agency still prefers short wave radios and face-to-face meetings over computers and more advanced technology. He says unlike e-mail, the short wave transmissions are almost impossible to track.