The man accused of attempting to kill author Salman Rushdie in New York two years ago now faces federal terrorism charges for his alleged support for Hezbollah, according to an unsealed indictment.
Hadi Matar already facing state charges of attempted murder and assault for the knife attack on Mr Rushdie.
The grand-jury indictment charges the New Jersey man with three terrorism counts, including carrying out an act of terrorism and providing material support to Hezbollah, a US-designated militant group that was founded by Iran in Lebanon during the early 1980s.
Mr Matar faces life in prison if found guilty on the federal charges.
"We allege that in attempting to murder Salman Rushdie in New York in 2022, Hadi Matar committed an act of terrorism in the name of Hizballah," Attorney General Merrick B Garland said in a written statement.
Iran's supreme leader at the time, Ayatollah Ruhollah Khomeini, pronounced a fatwa, or religious edict, calling upon Muslims to kill Mr Rushdie upon publication of his 1988 book, 'The Satanic Verses', considered blasphemous by some followers of Islam.
The acclaimed India-born novelist then spent a decade in hiding.
Prosecutors allege that Mr Matar was motivated in part by a 2006 speech given by Hezbollah Secretary General Hassan Nasrallah in which he endorsed the fatwa calling for Mr Rushdie's death.
The accused, who has Lebanese roots, pleaded not guilty to the state charges of second-degree attempted murder and assault.
He is being detained in a New York prison, awaiting trial.
Mr Matar was arraigned on the federal charges in the US District Court in Buffalo, New York.
His public defender, Nathaniel Barone, said his client would plead not guilty to the counts.
Mr Matar is a Shi'ite Muslim. Hezbollah is a Shi'ite Islamist group and shares the ideology of the Islamic Republic of Iran.
While Iran's pro-reform government of President Mohammad Khatami distanced itself from the fatwa in the late 1990s, it was never lifted.
Mr Rushdie was blinded in his right eye and his left hand was badly injured in the August 2022 attack.
It happened as he was about to deliver a lecture at an educational retreat near Lake Erie.
This year the writer released 'Knife: Meditations After an Attempted Murder' - a memoir recounting the assault.
