"There are no neat or easy answers here," Obama said in a speech in which he pledged anew to "clean up the mess at Guantanamo" that he said the nation had inherited from the Bush administration.

Obama conceded that some of the detainees would end up in U.S. prisons and insisted those facilities were tough enough to house even the most dangerous inmates.

Obama decried arguments used against his plans.

"We will be ill-served by the fear-mongering that emerges whenever we discuss this issue," he declared.

Speaking at the National Archives, Obama said he wouldn't do anything to endanger the American people.