President Obama is on the verge of breaking two key campaign promises in his troubled attempt to shut Guantánamo Bay — with plans to revive the military tribunal system set up by George Bush and to continue the indefinite detention of up to 100 inmates.

The moves, which have not yet been signed off by Mr Obama but look increasingly likely, are a result of his promise on his second day in office to shut the Guantánamo Bay prison within a year.

Since then, officials charged with working out how to shut down the prison concede that up to 100 of the 241 detainees remaining are either too dangerous to release or cannot be tried in a military or civilian court. The evidence against many of them is tainted because they were tortured, or involves sensitive issues of national security that cannot be revealed.

The latest Administration thinking has been decried by human rights groups who point out that as a presidential candidate, Mr Obama called the military tribunal system an enormous failure and condemned the indefinite detention of detainees as a gross breach of the US Constitution.

In addition to his pledge to shut Guantánamo, Mr Obama ordered a 120-day suspension of the military tribunal system, pending a review. Officials say that they now want a three-month extension, and have indicated that the hearings are likely to be restarted, with some modifications.

On the campaign trail, Mr Obama criticised the military tribunals because they drastically reduced the rights of defendants, with hearsay evidence permitted and even testimony produced under the harsh interrogation techniques the new Administration says amounted to torture.

Now Mr Obama’s lawyers are worried that they will struggle to try many detainees in federal court because a civilian judge could throw out much of the evidence, allowing allegedly dangerous men to walk free. Plans being worked on are to modify the tribunal system to increase the rights of defendants, but without giving them the full protections provided by the American legal system.

At a recent House hearing, Eric Holder, Mr Obama’s Attorney General, said that military tribunals could still be used but “would be different from those previously in place”.

Robert Gates, the Defence Secretary, who was asked last week if the Administration would abandon the Guantánamo tribunal system, said: “Not at all.” He added: “The commissions are still very much on the table.”

Jameel Jaffer, a lawyer for the American Civil Liberties Union (ACLU), said: “To revive a fatally flawed system that was designed to evade due process and the rule of law would be a grave error and a huge step backward.” Just as dismaying for such groups is the admission by Mr Gates to Congress last week that up to 100 detainees will probably have to be detained without trial, possibly in facilities on the US mainland.

Mr Gates said that 50 to 100 inmates “who we cannot release and cannot try” could end up being held without trial, probably on US soil. When asked about Mr Obama’s pledge to shut Guantánamo by January, Mr Gates said: “I think that question is still open.” Mr Gates did not specify whether such detentions would be temporary or indefinite, but acknowledged that congressmen and senators in all 50 states would oppose taking such detainees into their regions.

Anthony Romero, the executive director of the ACLU, said: “President Obama’s decision to close Guantánamo will be betrayed if we simply replace it with another detention centre on US soil that disregards the law.”

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