A lawyer for Captain James Yee on Tuesday said that despite  subsequently being cleared of all espionage charges, the case built by the US military and the media hype surrounding it had ruined his career prospects.

"The accusations have given him the persistent sense his career would never go anywhere,"  attorney Eugene Fidell said.

In his resignation letter submitted on Monday - but to take effect in January - Yee writes that he has been unfairly accused of grave offences under the Uniform Code of Military Justice and unjustifiably placed in solitary confinement for 76 days.

Irreparable damage

"Those unfounded allegations – which were leaked to the media – irreparably injured my personal and professional reputation and destroyed my prospects for a career in the United States Army," the letter said.

Yee was arrested in September 2003 and accused in October of breaking the rules governing the handling of classified information.

US authorities had suspected him of spying for the al-Qaida network at the Guantanamo detention centre, where about 600 detainees are held.

But charges against Yee were dropped after he had spent 76 days in detention.