On September 11, 2001, just hours after hijackers deliberately crashed passenger aircraft in attacks on the United States, a Kuwaiti teacher and imam named Suleiman Abu Ghaith met Osama bin Laden inside a cave in Afghanistan.

"We are the ones who did it," Bin Laden told Abu Ghaith, before asking him the next day to use his powers of oratory to send a videotaped "message to the world," Abu Ghaith testified on Wednesday in a surprise move at his trial on terrorism-related charges.

The video, and others like it, form the basis for the US government's case against Abu Ghaith, who would later marry one of bin Laden's daughters. Prosecutors say Abu Ghaith, 48, functioned as a spokesman and recruiter for bin Laden's Islamic militant group Al Qaeda and knew of plans to attack the US in the future.

Abu Ghaith told New York federal court jurors, however, that he simply followed talking points given to him by bin Laden and never intended to promote the group's agenda. He denied participating in any plots against Americans.

"Did you ever join Al Qaeda?" his lawyer, Stanley Cohen, asked him.

"No," said Abu Ghaith, the highest-profile bin Laden advisor to face charges in a US civilian court. His testimony, which had not been expected, came during the third week of the trial, which will conclude on Monday with closing arguments.

Abu Ghaith said he was invited to a meeting the next morning with Al Qaeda's senior leadership, including bin Laden and two of his most trusted lieutenants, Egyptians Ayman Al-Zawahiri and Mohammed Atef, a point Assistant US Attorney Michael Ferrara emphasized during cross-examination.

Ferrara questioned Abu Ghaith's claim that he was not speaking for Al Qaeda in the videos but for Muslims in general.

"Is it your testimony to this jury that when you say 'we' and 'us' in this speech, you are not referring to Al Qaeda?" Ferrara asked.

"I was not speaking on behalf of Al Qaeda," Abu Ghaith said through an interpreter.

His testimony offered a rare glimpse of the Al Qaeda leader's demeanor just hours after the devastating attacks on Sept 11, saying he seemed nervous rather than jubilant.

"What do you expect to happen?" Bin Laden asked Abu Ghaith, according to his testimony.

Abu Ghaith said he predicted that the US would not rest until it had accomplished two things: killing Bin Laden, and toppling the Taliban government in Afghanistan.

"He said, 'You are being too pessimistic,'" Abu Ghaith told jurors.

The US military and allies ousted the Taliban from government in 2001. Bin Laden was killed by US forces in May 2011 at his hideout in Pakistan.

Abu Ghaith acknowledged making several videos at bin Laden's request, including one in which he warned that a "storm of airplanes" was coming, but denied that he had any advance knowledge of other plots, such as the shoe bomb that Briton Richard Reid attempted to detonate aboard an airplane in 2002.

Some of the videos were an attempt to counter the propaganda against Muslims from the US, he said.

"My intention was not to recruit anyone," he said. "My intention was to deliver a message, a message that I believed in, that oppression, if it befalls any nation, any people, any category of people, that category must revolt at some point... And what happened was a result, as I understand, a natural result for the oppression that befell Muslims."

He said he only learned of the Sept 11 attacks via media reports. But he acknowledged under questioning from the prosecutor that before Sept 11 he had "heard something could happen," although he said he did not know any details.

Abu Ghaith said he traveled to Afghanistan for the first time in June 2001 to learn about the newly installed Taliban.

While there, he received a message from bin Laden asking for a meeting. Despite knowing that bin Laden was suspected of planning the attacks on two US embassies in Africa in 1998 and the suicide bombing of the USS Cole in 2000, he said he agreed, in part to avoid being "impolite."

"I wanted to see what he had, what it is that he wanted," he said.

"Did you ever discuss terrorist attacks?" Cohen asked.

"No," Abu Ghaith said. "Not at all."

But Ferrara, the prosecutor, expressed skepticism that Abu Ghaith would be willing to meet bin Laden despite his ties to previous attacks just to be polite.

Abu Ghaith also said that before the 2001 attacks, his contribution to bin Laden's organization consisted of giving religious speeches to fighters at training camps in Afghanistan.

Bin Laden, he said, told him that the camps were a "hard life," full of "weapons, training, roughness." He asked him to speak to the men to give them "merciful hearts," an explanation Ferrara sought to undermine.

"You're telling this jury that bin Laden asked you to speak at those training camps where men were armed and learning how to use guns because he wanted you to talk about mercy?" Ferrara asked, to which Abu Ghaith answered, "Yes." - Reuters