The suspected ringleader of the attack on the US consulate in Benghazi has appeared amid tight security at a US federal courthouse in Washington DC.
Ahmed Abu Khattala was captured by US forces in Benghazi on 15 June.
He denied a raft of terrorism-related charges. He says he was in Benghazi during the attack on the US consulate but that he did not take part.
The US ambassador to Libya, Chris Stevens, and three other people were killed in the September 2012 attack.
Mr Abu Khattala was charged with providing material support and resources to terrorists including himself; killing a person on a federal facility; and damaging property of the US by fire and explosives resulting in death.
Mr Abu Khattala, wearing a black, hooded top and black sweatpants, listened intently to the charges through an interpreter before pleading not guilty, the BBC's Beth McLeod in Washington reports.
The next hearing was set for 8 July.
American media reported that Mr Abu Khattala was brought to court in Washington from a US Navy warship where he had been held since being captured two weeks ago.
The US has described him as "key figure" in the attack on the consulate.
President Obama praised the raid which led to his capture earlier this month.
"When Americans are attacked, no matter how long it takes, we will find those responsible and we will bring them to justice," he said.
President Obama and then Secretary of State Hillary Clinton faced fierce criticism for not doing enough to prevent the attack.
Several Republican congressmen have called for Mr Abu Khattala and other terror suspects to be held at the US detention facility in Guantanamo Bay, Cuba.
Ahmed Abu Khattala
•Native of Benghazi in eastern Libya
•Construction worker by trade
•Spent several years in Col Muammar Gaddafi's notorious Abu Salim prison in Tripoli
•Formed his own small militia during the anti-Gaddafi uprising
•Denies any links to al-Qaeda but has expressed admiration for it
•Also denies any role in the attack on the US embassy in 2012, but eyewitnesses report him being there
•US state department says he is a senior leader in Islamist group Ansar al-Sharia