The two men entered guilty pleas to conspiracy and other charges in January. Their transfer comes after they provided testimony that prosecutors plan to use in the future against Nurjaman, the alleged mastermind, the Pentagon said in a statement.
Nurjaman is in custody in Guantanamo awaiting resumption of pre-trial hearings in January involving the Bali bombings and other attacks.
The two Malaysian men's transfers leave 27 detainees in custody at the U.S. naval base in Guantanamo Bay. President George W. Bush set up a military tribunal and prison after the Sept. 11, 2001 al-Qaida attacks on the U.S.
At peak, Guantanamo detained hundreds of men, most Muslim, in the U.S. military's “war on terror” after the Sept. 11 attacks.
Just two of the men at Guantanamo are serving sentences. U.S. prosecution of seven others currently facing charges has been slowed by legal obstacles — including those presented by the torture of the men in their first years under CIA custody — and logistical difficulties.
On Tuesday, U.S. authorities repatriated a Kenyan man, Mohammed Abdul Malik Bajabu, after 17 years at Guantanamo without charge.
His release leaves 15 other never-charged men awaiting release. The U.S. is searching for suitable and stable countries willing to take them. Many are from Yemen, a country split by war and dominated by an Iranian-allied militant group.
Amnesty International urged President Joe Biden to end the detention of those never-charged men before he leaves office. If not, the rights group said in a statement, "he will continue to bear responsibility for the abhorrent practice of indefinite detention without charge or trial by the U.S. government."