An Egyptian man accused of helping to plan the 1998 bombings of US embassies in Kenya and Tanzania has pleaded guilty in federal court in New York.
But a judge has not yet accepted a plea deal for Adel Abdul Bary, 54, that would see him serve 25 years in prison.
He was charged with conspiracy to murder and the use of weapons of mass destruction, among other counts.
More than 200 people were killed when the US embassies in Nairobi and Dar es Salaam were attacked in August 1998.
Bary was extradited from the UK in 2012 along with Mustafa Kamal Mustafa, also known as Abu Hamza.
He pleaded guilty on Friday to several lesser charges, including threatening to kill by means of explosive and conspiracy to murder US citizens abroad.
The judge has yet to rule on hundreds of other charges against him, including the murders of each person killed in the attacks and conspiracy to attack US national defence utilities.
On Friday, he wiped tears from his eyes and shook his head as he made the plea, according to Reuters news agency.
Judge Lewis Kaplan said he wanted to hear further arguments before the more serious charges could be dropped.
He gave lawyers for both sides one week to submit arguments on why he should accept the deal, which would see Bary sentenced to 25 years, potentially with credit for time served in the UK.
“You can well appreciate why I have questions in my mind,” Mr Kaplan said.
Bary would be permitted to withdraw the plea and proceed to trial if the judge rejects the deal.
He was originally set to go on trial in November, alongside two others charged in terrorism cases.