Randall Royer and Ibrahim al-Hamdi entered guilty pleas before the US District Judge Leonie Brinkema and agreed to cooperate with authorities investigating other members of the network.
The two from northern Virginia allegedly planned to help group members train at camps in Pakistan.
Royer faces a minimum of 20 years in prison for having discharged a full magazine of one of his weapons and transporting arms. Al-Hamdi faces at least 15 years for illegal possession of arms and explosives.
Royer confessed to helping five members of his network to enter a training camp in Pakistan run by the Lashkar-e-Taiba group. The training included use of rocket launchers destined for operations against India.
Lashkar-e-Taiba has been fighting Indian forces over the disputed territory of Kashmir for the past several years. Though banned in Pakistan, it clandestinely runs several camps.
"Our success in the war on terrorism depends on our ability to gain the cooperation of those who have information about the global terror network," US Attorney General John Ashcroft said in a statement.