Omar Khadr, a Canadian who was 15 when he was detained in Afghanistan over the killing of a US soldier, will face a military judge, as will suspected Al-Qaeda propaganda specialist Ali Hamza Ahmad al-Bahlul.
Lawyers for the two have condemned the military trials, while German
Chancellor Angela Merkel made a veiled call for Guantanamo to be closed ahead of her visit to Washington this week.
"An institution such as Guantanamo cannot and should not continue to exist like that in the long term," she told the German weekly magazine Der Spiegel.
US authorities continue to defend the holding of hundreds of detainees without charge at the camp as part of the "war on terror" declared after the September 11, 2001 attacks.
Trials frozen
But Guantanamo trials have been frozen by federal judges who are waiting for a Supreme Court ruling this year on the validity of the special tribunals created specifically to try the Guantanamo suspects.
The tribunal will first hear the case of Bahlul, a Yemeni, who was indicted in February 2004 for conspiracy in terrorist activities.
According to the charge, Al-Qaeda leader Osama bin Laden placed him in charge of producing videos to recruit and train new fighters.
During his first hearing in August 2004, Bahlul created confusion by demanding to defend himself. He has refused the help of any American lawyer, military or civilian.
Major Thomas Fleener, an army reservist appointed to defend Bahlul, called the military tribunals a "wholly illegitimate process" and said Bahlul's request was "simple".
"It's not outlandish to request the right to self-representation," said Major Fleener.
The military lawyer told reporters he suspected the request had been refused "essentially because it is inconvenient".
Under the tribunal rules, defendants are not allowed to be present when evidence that is considered classified is presented.
Khadr's case has become controversial because of his age.
The teenager was detained in Afghanistan in July 2002 on allegations that he killed a US military medic with a hand grenade during a battle.
Muneer Ahmad, a law professor at American University in Washington, said Khadr should not be tried as an adult, since the alleged offence was committed when Khadr was a minor.
Changing the rules
Ahmad expressed concern at the inexperience of the military lawyer representing the teenager, who is now 19.
"He is represented by a 31-year-old army captain who has never represented a defendant at trial in his life, even for charges of jaywalking," said Ahmad. "It would be laughable if the stakes weren't so high."
"Through torture, abuse and three years of illegal detention, this government has robbed Omar of his youth," said Ahmad. "Now, they are demanding his appearance before a kangaroo court, wholly lacking in fundamental principles of due process."
Khadr was born in Toronto and raised in Pakistan. His father, who was killed by the Pakistani army in 2003, was considered one of the key financiers of Bin Laden's network.
One of his brothers, also a terrorist suspect, was arrested last month in Canada at the US government's request.
Colonel Morris Davis, the chief prosecutor at the military tribunals, defended the Guantanamo trials.
"We face an enemy like we've never faced before," he said. "Some say we are changing the rules as we go along, but the law has to adapt to today's environment. Al-Qaeda and the Taliban are enemies the law didn't contemplate.
"The prosecution team is committed to holding full, fair, open and transparent trials. We're here to prosecute the terrorists who attacked us, not to persecute any religious beliefs. We've got nothing to be ashamed of."
Only nine of the 500 detainees currently held in Guantanamo have been formally charged.