Launching the most prominent 9/11-related terror trial held in New York to date, federal prosecutors said Suleiman Abu Ghaith had been one of bin Laden's key lieutenants in the days and months after the September 11, 2001 attacks which left 3,000 people dead.

The Manhattan trial is taking place just streets from where the World Trade Center was reduced to burning rubble by two airliners hijacked by Al-Qaeda suicide attackers.

Abu Ghaith is on trial for conspiracy to kill Americans, conspiracy to provide support and providing material support to terrorists.

The 48-year-old from Kuwait pleads not guilty to all three charges. He faces life in prison if convicted.

He is the most senior alleged Al-Qaeda member to face trial in a US federal court rather than at Guantanamo Bay, which the White House has promised to close.

Wearing a dark suit, he sat impassively as prosecutors played the video in which he sat next to bin Laden and the current leader of Al-Qaeda, Ayman al-Zawahiri, in Afghanistan on September 12, 2001.

He was similarly unmoved as the court watched a clip of him lecturing and gesticulating, dressed in a black turban in Afghanistan.

He spoke only to confirm when asked by Judge Lewis Kaplan that he understood proceedings, and listened to simultaneous translation provided on an ear piece.

His salt-and-pepper beard was neatly trimmed and although balding, dark curls tapered into his neck.

By the afternoon session he had removed a blue silk tie and unbuttoned the top button of his shirt.

Abu Ghaith is not accused of involvement in the 9/11 attacks, but of recruiting personnel for Al-Qaeda, or what the prosecution called its "very lifeblood".

The prosecution also claims he was complicit in the December 2001 shoe-bombing plot to bring down an airliner flying from Paris to Miami.

- 'Trusted' Al-Qaeda insider -

US prosecutor Nicholas Lewin described Abu Ghaith as a "trusted" Al-Qaeda insider who quickly met bin Laden after leaving Kuwait for Afghanistan in spring 2001.

He spent the summer of 2001 speaking to hundreds of young Al-Qaeda recruits at Afghan training camps, preparing them for war and earning his stripes.

Then after the 9/11 attacks, his job changed.

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"Literally hours after the attacks, Osama bin Laden turned to this man," said Lewin, standing behind the defendant and pointing at him.

The Al-Qaeda terror chief wanted this "important religious scholar" and "inspirational and charismatic speaker" to recruit men globally for jihad, he added.

"Osama bin Laden asked that man to deliver Al-Qaeda's murderous decree to the world," Lewin told the court.

"What did the defendant do? He agreed."

"You don't sit outside a cave on September 12, 2001 with the most wanted man on earth unless you're inside Al-Qaeda at the very, very top," added Lewin.

Abu Ghaith "sat at the right hand of Osama bin Laden," Lewin said, quoting liberally from Abu Ghaith's proclamations threatening a "storm of airplanes".

Married to bin Laden's daughter Fatima, US prosecutors say Abu Ghaith worked for Al-Qaeda until 2002, when he fled Afghanistan after the US invasion for Iran.

He appeared in follow-up videos in October and November 2001, an AK-47 assault rifle at his feet, threatening further attacks in a "storm of airplanes."

- Shoe bomb evidence key -

Key will be evidence linking him to the December 2001 shoe bomb plot, which the defense says does not exist.

Defense attorney Stanley Cohen on Wednesday suggested to the 13-women and five-men jury that the prosecution case was fantasy: "You've just been to the movies."

Gently touching his client on the shoulder Cohen said: "This is not Osama bin Laden".

"This is Suleiman Abu Ghaith. He's a Muslim. He's an Arab. He's from Kuwait. He's a husband and a father. Yes he's an imam, a talker. An ideologue."

"At the end of the day there's really no evidence," Cohen said.

The first key witness will be 33-year-old Saajid Badat, a convicted co-conspirator in the shoe-bomb plot who will testify by video from London on Monday.

The trial is expected to run for most of March.

It is one of a series of terror cases transferred to New York as Obama has promised to close down the military prison at Guantanamo Bay.