The United States has charged a Yemeni man with conspiracy, making him the fourth prisoner held at the US naval base at Guantanamo Bay to face trial before a military tribunal.
Salim Ahmed Hamdan is charged with one count of conspiracy to commit murder, attacks on civilians and terrorism, the Pentagon said.
His case was referred to a tribunal - formally called a military commission - of five US officers, but no trial date was set, the Pentagon said.
The government will not seek the death penalty against him, said a Pentagon spokesman.
The Pentagon said Hamdan provided security for al-Qaeda leader Osama bin Laden and other top members of the network.
The US military commissions - the first of their kind since World War Two - have faced criticism from human rights groups who argue the rules are rigged to hamstring defence lawyers and produce convictions.
The Pentagon has pledged "full and fair" trials.
The same tribunal will handle the trials of the other three Guantanamo prisoners charged by the United States.
Australian David Hicks was charged in June with three counts: conspiracy to commit war crimes, attempted murder and aiding the enemy. Ali Hamza Ahmed Sulayman al-Bahlul of Yemen and Ibrahim Ahmed Mahmoud al-Qosi of Sudan were charged in February with a single count each of conspiracy to commit war crimes.
No trial dates have been set in those cases, although the Pentagon has said it hopes to conduct a trial by the end of the year.