John P. Cronan, an assistant United States attorney, said in court that Mr. Abu Ghaith had spoken at length with United States law enforcement officials after his arrest by federal authorities on Feb. 28. Mr. Cronan cited a 22-page document detailing his statements but did not characterize the statements, which were not made public.
The appearance of Mr. Abu Ghaith before Judge Lewis A. Kaplan of United States District Court, in the cavernous, wood-paneled ceremonial courtroom in Lower Manhattan, just blocks from ground zero, the site of the Sept. 11 attack on the World Trade Center, was not without symbolism. But details of both the defendant’s role in Al Qaeda and his arrest remained unclear.
Slight, trim and balding, with a manicured gray beard, Mr. Abu Ghaith was led into the courtroom wearing handcuffs and a blue prison smock as about a dozen United States marshals — an unusually large complement — provided security. His handcuffs were removed for the proceeding.
Mr. Abu Ghaith said little beyond a few one-word replies to questions from the judge.
Philip L. Weinstein, one of three lawyers the judge appointed to represent him, entered a plea of not guilty on his behalf during the proceeding, which lasted less than 20 minutes.
Mr. Cronan asked that Mr. Abu Ghaith be held without bail. Mr. Weinstein did not challenge the request but left open the possibility of making a bail application later. Mr. Cronan said the government would take three weeks to present its case at trial, but no date was set.
Judge Kaplan summarized the single charge facing Mr. Abu Ghaith and explained his rights. The proceedings were translated into Arabic for Mr. Abu Ghaith, who listened on headphones.
Justice Department officials described him as a propagandist. They said they believed that he had not had an operational role in Al Qaeda for years and that he did not participate in the attacks on Sept. 11, 2001. But one law enforcement official said Mr. Abu Ghaith, 47, was the most senior Qaeda figure to face criminal trial in New York. He was married to Bin Laden’s daughter Fatima, and the indictment alleges a working relationship with Bin Laden, who was killed in Pakistan by United States forces in 2011.
“Among other things, Abu Ghaith urged others to swear allegiance to Bin Laden, spoke on behalf of and in support of Al Qaeda’s mission, and warned that attacks similar to those of Sept. 11, 2001, would continue,” the indictment said.
