Washington - A US man pleaded guilty on Thursday to trying to help the Islamic State of Iraq and Syria jihadist group and now faces 15 years in prison and a $250 000 fine, officials said.
Donald Ray Morgan, aged 44, was arrested in early August at JFK International Airport in New York on an outstanding firearms charge, and investigators looked into his recent travels.
"He travelled overseas with intentions to join the violent terrorist group, ISIS in Syria", FBI special agent in charge John Strong said in a statement.
"American citizens who support terrorist organisations must be held accountable for their actions."
Morgan pleaded guilty to attempting to provide material support to a designated foreign terrorist organisation and possession of a firearm by a felon.
According to court documents, Morgan knowingly tried to provide support, including his own services between January and August to ISIS.
On at least one occasion Morgan, from North Carolina, unsuccessfully tried to travel from Lebanon to Syria to join ISIS fighters, prosecutors said.
Morgan used social media and an interview with NBC News to express his support for the jihadists and for violent terrorist activities.
In a Twitter message seen by the FBI at the end of July, he allegedly wrote: "Killing our enemies and beheadings are justified."
In his interview with NBC, filmed in Beirut and broadcast on 3 September, Morgan said he'd bought a ticket "with the intent of entering Syria [and] either joining up with food and medical aid convoys or directly with ISIS."
"Today's plea is a sad reminder that those who wish to aid foreign terrorist organisations can come from any community and from any background", US Attorney Ripley Rand said.
Morgan was initially arrested on 2 August 2014, at JFK airport on a federal indictment for possession of a firearm by a felon.
The firearm offense dates back to January 2012 and carries a potential 10-year prison term.
Sentencing is set for 18 February 2015.