Basit Sheikh, 29, is charged with providing material support to a terrorist group for attempting to join Jabhat al-Nusra, which the US government declared a terrorist organisation.
Hewas arrested in November at a North Carolina airport at the start of what prosecutors say was a journey to fight in Syria's civil war, which has killed more than 100,000 people.
Federal prosecutors wanted more time before trying Sheikh, arguing the Central Intelligence Agency, National Security Agency and other intelligence agencies needed time to look through data they might have while protecting spying sources and methods.
The FBI says it has evidence collected by secret informants who corresponded online with Sheikh showing that he expressed a desire to join and fight with Jabhat al-Nusra. The FBI said he planned to sneak into Syria to join the fight against forces loyal to Syrian President Bashar Assad.
The judge last week rejected an attempt to free Sheikh on bail after deciding he was a flight risk and a danger to the community.
Sheikh has no criminal record, but during a November hearing his mother testified that the 29-year-old likely suffered from anxiety and depression, needed psychiatric help, lacked a job and spent all of his time on the Internet, the judge wrote.