NEW YORK – Sulaiman Abu Ghaith, 47, was turned over to US officials in Jordan within the last week while on his way to Kuwait, authorities have said.
A Kuwaiti preacher, Mr Abu Ghaith is Bin Laden’s son-in-law, officials said.
The Obama administration’s decision to try him in civilian court has been criticised by Republicans.
They say Mr Abu Ghaith should be sent to the US detention centre at Guantanamo Bay, Cuba, to face a military tribunal.
Bin Laden was killed in a May 2011 raid on his hideout in Pakistan by a team of US commandos.
On Friday, Mr Abu Ghaith pleaded not guilty to conspiracy to kill US nationals, in a federal courtroom in lower Manhattan about half a mile (0.8km) from the site of the 11 September 2001 attack on the World Trade Center.
Prosecutor John Cronan told the court that Mr Abu Ghaith had given an “extensive post-arrest statement” totalling 22 pages, but did not give details.
A trial is set to start on 8 April and is expected to last about three weeks.
“Sulaiman Abu Ghaith held a key position in al-Qaeda, comparable to the consigliere in a mob family or propaganda minister in a totalitarian regime,” said FBI Assistant Director-in-Charge George Venizelos.
“He used his position to threaten the United States and incite its enemies.”
In court filings, US prosecutors say Mr Abu Ghaith served alongside Bin Laden from May 2001 to 2002, speaking on behalf of al-Qaeda and warning that attacks similar to 9/11 would continue.
Specifically, on 12 September 2001, he appeared with Bin Laden and Ayman al-Zawahiri to warn the US that a “great army is gathering against you” and called upon “the nation of Islam” to do battle against “the Jews, the Christians and the Americans”, prosecutors wrote.
A one-time teacher and mosque preacher in Kuwait, Mr Abu Ghaith was stripped of his Kuwaiti citizenship after 9/11.
In 2002, as the US launched a war in Afghanistan to defeat al-Qaeda and its Taliban hosts, Mr Abu Ghaith fled al-Qaeda’s Afghanistan base for neighbouring Iran, prosecutors allege.
He was reportedly smuggled into Iran with two other senior al-Qaeda leaders. Unconfirmed reports said they were held under house arrest by Iran’s Islamic Revolutionary Guard Corps.
US authorities have released little information about Mr Abu Ghaith’s capture.
Reports suggest he crossed into Turkey from Iran and was arrested by the authorities in the Turkish capital Ankara. (BBC)