Captain James Yee, a West Point graduate, was promised a "rosy career" in the military, his attorney Eugene Fidell told AFP.

But the accusations have given him "the persistent sense his career would never go anywhere," the lawyer explained.

In his resignation letter that was submitted Monday but will take effect only in January, Yee writes that he was "unfairly accused of grave offenses" under the Uniform Code of Military Justice and unjustifiably placed in solitary confinement for 76 days.

"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 on October 10 of breaking rules governing the handling of classified information.

US authorities had suspected him of spying for the al-Qaeda terror network at the detention center at a naval base at Guantanamo Bay.

The charges were dropped after he had spent 76 days in detention.

WAR.WIRE