LONDON: A British army interpreter working for the commander of international forces in Afghanistan betrayed his country by spying for Iran, prosecutors said Monday.

Daniel James, who was born in Tehran, was a "Walter Mitty" style fantasist who was embittered because he thought he should have been promoted and that he was a victim of racism, they said.

"I am at your service," the 45-year-old allegedly said in a code message to an Iranian military attache in Kabul, according to prosecutor Mark Dennis, who said James was in a "unique position" to divulge sensitive information.

"During the latter part of 2006, the defendant''s loyalty to this country wavered and his loyalties turned to Iran, the country of his birth," said Dennis on day one of the trial at the Central Criminal Court, or Old Bailey, in London.

"He turned his back on those with whom he was serving in Afghanistan and sought to become an agent for a foreign power."

James denies charges under the Official Secrets Act of communicating information useful to an enemy and collecting such information on a computer memory stick.

But the prosecutor said that, after being sent to Afghanistan in March 2006, he became "aggrieved and somewhat bitter at his lack of promotion, particularly given his work in Afghanistan," Dennis said.

"He began to complain to others about what he perceived as discrimination against him in the army -- linking racist attitudes to his lack of promotion," said Dennis.

Specifically he was allegedly in contact with Mohammad Hossein Heydari, an Iranian military assistant based at Tehran''s embassy in Kabul. The two men exchanged emails and "many telephone conversations," he said.

When he was arrested in December 2006, he was found with a computer flash drive containing two confidential NATO files.