The man, identified as Asif William Rahman, was arrested by the FBI this week in Cambodia and was due to make his first court appearance in Guam.
He was indicted last week in U.S. court in Virginia on two counts of willful transmission of national defense information — felony charges that carry significant prison sentences.
It was not immediately clear whether Rahman had a lawyer or which federal agency employed him, but officials say he had top secret security clearance.
The charges stem from the documents appearing last month on a channel of the Telegram messaging app. The documents noted that Israel was still moving military assets in place to conduct a military strike in response to Iran's blistering ballistic missile attack on Oct. 1.
Israel carried out a retaliatory attack on multiple sites in Iran in late October.
