"They are not done yet, and they will not be done until there is more than one death," a Muslim adviser to the military told The New York Times. Some are being forced-fed.
The adviser said he feared there may be suicides, the Times reported Wednesday.
The cause for the hunger strike is disputed, with detainees, through their lawyers, saying guards handled copies of the Koran disrespectfully when conducting cell searches Feb. 6, the Times said. Prison officials dispute that.
Both military officials and inmates' lawyers told the Times the underlying basis of the turmoil is a growing sense among prisoners, some of whom have been held without trial for more than 11 years, that they will never go home.
President Obama made closing the prison a top priority when he entered the White House in 2009 but put that in abeyance in the face of congressional opposition to his plan to move detainees to a supermax prison in the United States.
The prisoners "had great optimism that Guantanamo would be closed," Gen. John F. Kelly, head of the U.S. Southern Command, told Congress recently. "They were devastated when the president backed off -- at least their perception -- of closing the facility."
In January 2012, Obama signed legislation restricting prisoner transfers. Early this year, the Obama administration reassigned but did not replace the diplomat who had negotiated the transfers.
"President Obama has publicly and privately abandoned his promise to close Guantanamo," said Carlos Warner, a lawyer representing one of the hunger strikers kept alive by being force-fed. "His tragic political decision has caused the men to lose all hope. Thus, many innocent men have chosen death over a life of unjust indefinite detention."
"The situation is not sustainable," Kenneth Wainstein, the top national security official at the Justice Department in the George W. Bush administration, told the Times. "There are strong, principled arguments on both sides, but all of us across the spectrum have to acknowledge that this is far from an ideal situation and we need an exit strategy."
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