Washington  - The former driver for Osama bin Laden pleaded not guilty to terrorism-related charges on Monday as the first trial under US President George W Bush's controversial military commissions got under way in Guantanamo Bay, Cuba.

Salim Hamdan, a Yemeni national, has been charged with conspiracy and providing material support for terrorism and faces a maximum sentence of life in prison if convicted.

Hamdan is alleged to have served as bin Laden's driver and bodyguard before his capture in 2001 and transfer to the US detention centre at the naval station in Cuba the following year.

Hamdan alleges he was abused during intense interrogations while in US custody, and has been among the most active Guantanamo detainees challenging the legal process in federal court, including in a key ruling by the US Supreme Court in June 2006 that US President George Bush's commissions were unconstitutional and violated the Geneva Conventions.

The decision forced the White House to revamp the process and get congressional approval, which took place several months later.

Hamdan's trial is seen as the first test of the military commissions since they were first established by Bush seven years ago. The Pentagon has charged 20 detainees, and that number is expected to climb to 80 of the 275 detainees who remain locked up at Guantanamo.

Human rights groups have said that the tribunals do not provide the detainees with the rights afforded by US civilian courts and are designed to produce convictions.

"These are second-class trials to which the US government would not subject its own nationals," Amnesty International said Friday.

The defendants have military-appointed attorneys and are permitted to seek private counsel. The US military maintains the trials are fair because defendants are allowed to summon witnesses to testify on their behalf, and have access to all of the evidence prosecutors can display in court.

The trial of the alleged mastermind of the September 11, 2001, terrorist attacks, Khalid Sheikh Mohammed, and four other defendants in the death penalty cases could get under way as early as September. Mohammed declared during a hearing in June that he wanted to be martyred. (dpa)