State Department spokesman Philip Crowley said that the arrest culminated a three-year investigation and that Secretary of State Hillary Rodham Clinton has ordered a "comprehensive damage assessment" to determine what information may have passed to the Cubans.
The Myerses' arrest could affect congressional support for easing tensions with Cuba dating to the Cold War. Two months ago, the Obama administration took steps to relax a trade embargo imposed on the island nation in 1962.
David Kris, assistant attorney general for national security, described the couple's alleged spying for the communist government as "incredibly serious."
Court documents indicate the couple received little money for their efforts, but instead professed a deep love for Cuba, Castro, and the country's system of government.
The documents describe the couple's spying methods changing with the times, beginning with old-fashioned tools of Cold War spying: Morse code messages over a short-wave radio and notes taken on water-soluble paper. By the time they retired from the work in 2007, they were reportedly sending encrypted e-mails from Internet cafes.
The criminal complaint says changing technology also persuaded Gwendolyn Myers to abandon what she considered an easy way of passing information, by changing shopping carts in a grocery store. The document quoted her as saying she "wouldn't do it now. Now they have cameras, but they didn't then."
Authorities say her comments came during a series of meetings with an undercover FBI agent posing as a Cuban spy in April. The Myerses fell for the ruse, authorities say, sharing with the agent their views of Obama administration officials that had recently taken over responsibility for Latin American policy and accepting a device to encrypt future e-mail.
The couple, who live in an apartment building in northwest Washington, were arrested Thursday and pleaded not guilty yesterday in US District Court. They were ordered held in jail until a detention hearing scheduled for Wednesday. A call to their home telephone was not answered. Their lawyer, Thomas Green, declined to comment.
