Guantanamo Bay's chief prosecutor says the US has a strong case against Australian detainee David Hicks and is soon to bring charges against him.
David Hicks has been at Guantanamo Bay for five years
Colonel Morris Davis also accused Mr Hicks' lawyer of circulating "half truths" to defend his client.
Protest are being held in Australia to mark the fifth anniversary of the arrival at Guantanamo Bay in Cuba of Mr Hicks and the first detainees.
PM John Howard says he has again raised concerns about Mr Hicks with the US.
Mr Howard said that, during a telephone conversation, he left US President George W Bush "in no doubt" of his government's view that Mr Hicks should be charged as soon as possible.
Colonel Davis told the Australian Broadcasting Corp that Mr Hicks would be among the first to be charged when new rules over the trials come into effect, later this month.
"I anticipate within two weeks of the rules coming out we will start charging some of the individuals and David Hicks, I believe, will be among the first that we charge," he said.
David Hicks and other detainees may face new trials soon
He said he expected Mr Hicks could face trial within six months.
Col Davis also urged Australians not to believe without question what Mr Hicks' lawyer, Major Michael Mori, had been saying.
"I hope the Australian people aren't so gullible as to step in everything that Major Mori has been spreading," he said.
"And if they do step in it, they need to wipe their feet before they go into the house, because we contend a lot of the evidence has been half truths."
Col Davis said Mr Hicks had experience in Kosovo and Kashmir as well as al-Qaeda training camps.
"From my understanding, when 9/11 happened he was out of the country, but once he saw the US had been attacked he made a conscious choice to try to get back to Afghanistan, report in to a senior al-Qaeda leader and, in essence, say: "I'm David Hicks and I'm reporting for duty".
Hitting back, Major Mori said he was disappointed "they would feel that desperate that they would attack me personally, they have stooped to a new low."
"They want to distract people from the real issue, which is, is David going to get a fair trial?"
David Hicks, 31, was arrested in Afghanistan in late 2001 and has been held at Guantanamo Bay since 11 January 2002.
He was charged with conspiracy, attempted murder and aiding the enemy.
But these charges were dropped when the US Supreme Court ruled that military tribunals set up to try the Guantanamo Bay detainees were unlawful.
Both Mr Hicks' lawyers and family have been pushing for a resolution to his situation, saying they fear for his mental health after such a long time in detention without trial.