US President Barack Obama on Friday restarted a Bush-era military trial system for a small number of Guantanamo detainees, reviving a method of prosecution he once assailed as flawed but with new legal protections for terror suspects.

In a three-paragraph White House statement, Obama announced the decision that already has drawn criticism from liberal groups, arguing that it will ensure a legitimate forum to prosecute alleged terrorists being held at the detention centre at Guantanamo Bay, Cuba.

“This is the best way to protect our country, while upholding our deeply held values,” he said in a statement.

For now, the military trials will remain on hold as Obama changes the legal system that is expected to try fewer than 20 of the 241 detainees now being held at Guantanamo.

Obama said that immediate rule changes governing the trials will begin to bring them in line with the rule of law, most significantly by altering some rules of allowable evidence. Obama also is asking Congress to change the 2006 law creating the current, on-hold tribunal system to enact more sweeping reforms. Pentagon lawyers were filing a continuance request with the military commissions judge seeking a 120-day delay in trials to give it time to enact at least the initial rule changes.