He is identified as a major al-Qaida core official by the New America Foundation think tank in Washington.
King said Abu Ghaith was involved in the planning in the 9/11 attacks against the World Trade Center and Pentagon.
Tom Lynch, a research fellow at the National Defense University in Washington, described Abu Ghaith as one of a small handful of senior al-Qaida leaders "capable of getting the old band back together and postured for a round of real serious international terror."
"His capture and extradition not only allows the U.S. to hold - and perhaps try - a reputed al-Qaida core survivor, further tarnishing the AQ core brand, but it also points to the dangers for those few remaining al-Qaida core refugees," Lynch said.
Abu Ghaith's trial will make one of the relatively few prosecutions of senior al-Qaida leaders on U.S. soil.
Charging foreign terror suspects in American federal courts was a top pledge by President Barack Obama shortly after he took office in 2009 - aimed, in part, to close the detention center at Guantanamo Bay, Cuba.
Since 9/11, 67 foreign terror suspects have been convicted in U.S. federal courts, according to watchdog group Human Rights First, which obtained the data from the Justice Department through a Freedom of Information request.
