Defense Secretary Austin will bid farewell Friday following a term that included three major military crises, a global pandemic and a brush with cancer.
It's the latest development in the U.S. military's struggle to bring to justice the man charged with planning the Sept. 11 attacks on the United States.
U.S forces are still needed in Syria to prevent ISIS from reconstituting as a major threat following Assad's ouster, Defense Secretary Lloyd Austin said.
The decision puts back on track agreements that would have the three men plead guilty in exchange for being spared the possibility of the death penalty.
U.S. officials are also continuing their search for Austin Tice, an American journalist and Marine Corps vet who disappeared 12 years ago near Damascus.