Singapore man Haniffa Bin Osman, 55, was the latest person to plead guilty in the investigation which saw undercover agents track the alleged arms dealers from the eastern port of Baltimore to the South Pacific US territory of Guam.
"The disruption of the supply chain of this organization should reassure the public that the US government is committed to dismantling terrorist groups worldwide," said FBI special agent William Chase.
Four Indonesians and Osman have now pleaded guilty to charges stemming fom the investigation, from conspiracy to support a terrorist organization to attempting to illegally export arms.
They all face significant jail terms.
A sixth person, Sri Lankan Thirunavukarasu Varatharasa, goes on trial next month on charges of conspiracy, attempting to export arms, money laundering, and illegal possession of weapons.
"Keeping sophisticated US weapons from falling into the hands of terrorists has never been more important," said James Dinkins, special agent for the US I