He had wanted grenade launchers and other weapons delivered to the Tigers, the Baltimore Sun newspaper said.
Subandi found himself involved in an elaborate sting operation last year designed by federal agents in Maryland.
Subandi, who had an initial role in the negotiations over the restricted weapons, but bailed out early over a money dispute, was still "without conscience," in the words of Assistant U.S. Attorney James Warwick.
He pleaded guilty in March.
As part of the sting operation, Subandi tried to acquire restricted night-vision goggles to sell to the Indonesian army, as well as machine guns and other American military weapons to offer to the Tamil Tigers in Sri Lanka, court papers show.
Customs agents have said that combating the illegal export of military technology is among the highest priorities of U.S. Immigration and Customs Enfo