The U.S. military has dismissed war crimes charges against five Guantanamo Bay detainees after a prosecutor for another detainee resigned in September, alleging the military was suppressing evidence favourable to the defence.

The military's unprecedented move was directly related to accusations brought by the man who was to bring all five prisoners to justice, including one accused of plotting to detonate a "dirty bomb" in the United States.

Lt.- Col. Darrel Vandeveld had been appointed the prosecutor for all five cases, but at a pretrial hearing for a sixth detainee earlier this month, he openly criticized the war crimes trials as unfair.

Vandeveld said the military was withholding exculpatory evidence from the defence, and was doing so in other cases.

A military spokesman, Joseph DellaVedova, said in San Juan, Puerto Rico, that the military might renew the charges later against the five now being held at the U.S. military prison in Cuba. They are Noor Uthman Muhammed, Binyam Mohamed, Sufyiam Barhoumi, Ghassan Abdullah al Sharbi and Jabran Said Bin al Qahtani.

But despite the decision, announced Tuesday, there are no plans to free the men. New trial teams are taking another look at the evidence, the military said, and after consulting with intelligence agencies will recommend whether or not to reinstate charges.

Renewed charges

Clive Stafford Smith, a civilian lawyer representing detainee Binyam Mohamed, said he has already been notified that charges against his client would be reinstated.

"Far from being a victory for Mohamed in his long-running struggle for justice, this is more of the same farce that is Guantanamo," Stafford Smith said. "The military has informed us that they plan to charge him again within a month, after the election."

Lt.- Col. Bryan Broyles, who represents one of the prisoners whose charges were dropped, said, "The military might be preparing the tribunals to face increased scrutiny following next month's presidential election."

The chief prosecutor for the U.S. military tribunals, Col. Lawrence Morris, will review the evidence in each case and make recommendations.

Presidential hopefuls Sen. John McCain and Sen. Barack Obama have both said they want to close Guantanamo.

Defence secretary urges future president to act fast to close prison

U.S. Defence Secretary Robert Gates said the next president should move quickly to close the prison, adding that it will not be closed before the end of President George W. Bush's tenure.

Gates, who has previously advocated for the prison's closure since taking his post in 2006, told reporters on Tuesday that Guantanamo was "a real liability for the United States."

Asked to state whether the prison would be closed before the Bush administration leaves office Jan. 20, Gates replied: "No, regretfully."

"This is an issue that'll have to be addressed early on by a new administration," Gates said.

The Bush administration had concluded that legislation would be required to close the facility, he said, but it was unlikely that it would get passed amid the turbulent political climate ahead of the Nov. 4 presidential election.

The type of legislation that would be required would, for example, have to include rules on preventing Guantanamo inmates from emigrating to the United States.

The military prison has been roundly criticized by international observers, human rights groups and governments overseas for failing to meet international legal standards.

With files from the Assocated Press and Reuters