WASHINGTON: Majid Khan, a protege of September 11 mastermind Khalid Sheikh Mohammed, has pleaded guilty at a Guantanamo military tribunal under a deal with US authorities that will require him to testify against other terror suspects.

Khan, a Pakistani national, pleaded guilty to a raft of charges in a landmark case that analysts said could speed trials against those linked to the 2001 attacks, which prompted the US-led "war on terror".

Khan, 32, who lived legally in America and graduated from a US high school, denied ever meeting or speaking with slain Al-Qaeda leader Osama bin Laden, but admitted to taking part in a "conspiracy" in Pakistan, Thailand and Indonesia.

"This agreement doesn't guarantee me that I'll go free. Basically I'm making a leap of faith, that's all I can do," Khan, wearing a dark suit and pink tie, told military judge Colonel James Pohl.

Khan, who has spent the last nine years behind bars and faced possible life in prison, will be sentenced to no more than 19 years under the plea agreement, which requires him to cooperate with US authorities.

In exchange for the lighter sentence, Khan would testify against other "high value" detainees, including Mohammed and four others implicated in the 9/11 plot to crash airliners into the World Trade Center and the Pentagon, which saw a fourth hijacked plane plunge into a field in Pennsylvania.

To ensure that Khan fulfills his side of the bargain, the sentence will not be handed down for four years, until February 29, 2016.

It is the first plea bargain among 14 Guantanamo Bay detainees the US military classifies as "high value."

"It's part of a strategy of building more solid cases against the handful of defendants that the government plans to try before the commissions," said Jonathan Hafetz, a lawyer who has represented other Guantanamo detainees.

More than 10 years after the 9/11 attacks, Mohammed and four co-defendants accused of plotting the strikes are still awaiting trial at the prison, part of a US naval base in Cuba.

At Wednesday's hearing, Pohl rejected a defense request that the terms of the plea agreement be kept secret for security reasons, saying "the nature of plea and the nature of information are already in the public domain."

Khan was convicted of working under Mohammed's direction to plan explosions of fuel tanks at US gasoline stations and of plotting to assassinate former Pakistani president Pervez Musharraf.

He also pleaded guilty to delivering funds for a bomb attack at a Marriott hotel in Jakarta, Indonesia that killed 11 people in August 2003.

Round-faced with a small goatee and glasses, Khan lived in the United States for seven years before his arrest in Pakistan in 2003.

US President Barack Obama -- criticized for failing to live up to his promise to shut down the Guantanamo Bay detention facility by 2010 -- could benefit from the plea deal as he seeks a new term in November elections.

"If Khan provides information on KSM and others, as has been suggested was part of the deal, it will no doubt speed up the prosecutions," said Karen Greenberg, a terrorism expert at Fordham Law School, referring to Mohammed, who had been scheduled to be arraigned earlier this month.

Such testimony, she said, "will break through the barriers presented by evidence obtained through torture, as this information will be presented in the present time and in a legal proceeding."

But Brigadier General Mark Martins, chief military commissions prosecutor, said he did not believe there was anything political about the plea deal, saying: "This system is fair and not politically driven."

Over the years, 779 inmates have been detained at Guantanamo, most without charge or trial. Most have been transferred to their home countries or third countries in recent years and released.

Today, 171 people are still there in limbo, including 89 detainees who have been cleared for release but are still in custody because of a law passed by the US Congress.

For the other detainees who remain, pleading guilty may be the only way to guarantee that they one day leave the facility.

"The irony is that if you're charged with a crime and make a plea deal, you know you'll be released someday and have some idea when," said David Remes, who has represented several detainees.

"But if you're not accused of a crime, you don't know whether you'll ever be released, much less when. The system is upside-down."

Khan was imprisoned in a secret CIA jail for three years before being transferred to Guantanamo in 2006, where he was held in Camp VII with other "high value" detainees.

Rear Admiral David Woods, the director of the facility, said Khan had "very recently" been transferred to an extension of Camp VII, where he will have the option of taking part in a "socialization program."