Salim Hamdan, a Yemeni, has been in custody for nearly six years
A US judge has ruled that the first war crimes trial at the Guantanamo Bay detention centre, involving Osama Bin Laden's former driver, can go ahead.
Judge James Robertson dismissed a claim from lawyers for Salim Hamdan, a Yemeni, that it should be stopped while he challenged the process's legality.
The ruling came after a military judge at Guantanamo denied a postponement.
Last month, the US Supreme Court ruled detainees had to be able to challenge their detention in civilian courts.
It said the 270 men currently being detained at Guantanamo had "the constitutional privilege of habeas corpus" - the right for suspects to be heard by an independent judge on the legality of their detention.
After hearing more than two hours of arguments in Washington, Judge Robertson agreed with US government lawyers that Mr Hamdan's military tribunal could begin as scheduled on Monday without contradicting the Supreme Court.
Deputy Assistant Attorney-General John O'Quinn said a law passed by Congress in 2006 allowed such challenges to be taken to the US Court of Appeals only after the trial had taken place.
"Hamdan is to face a military commission designed by Congress based on guidelines handed down by the Supreme Court," he said.
Mr Hamdan's lawyers said they had expected a different outcome and had not yet decided whether to appeal.
"It is bad news for us - we are very disappointed," one of them told the AFP news agency.
Mr Hamdan, 37, who has been in custody for nearly six years, is charged with conspiracy and supporting terrorism, and faces life in prison if convicted.
In December, a US military judge said there was credible evidence he had served as the al-Qaeda leader's bodyguard, and sometimes picked up and delivered weapons.
Mr Hamdan has acknowledged working for Bin Laden in Afghanistan from 1997 to 2001 for $200 (£99) a month, but denies being part of al-Qaeda or taking part in any attacks.