The Obama administration prefers a civilian trial for the alleged 9/11 mastermind, but says that in the face of public and political opposition it must be open to a military tribunal.
In an interview published Monday in The New York Times, Attorney General Eric Holder said, "I have to be more forceful in advocating for why I believe these are trials that should be held on the civilian side."
However, Holder did not rule out a military trial for Khalid Sheikh Mohammed, saying, "You have to be flexible."
Vice President Joe Biden defended the White House from critics of its approach to prosecuting accused terrorists, saying in interviews aired Sunday that it is not yet clear where Mohammed and four other Sept. 11 suspects held at the U.S. military prison at Guantanamo Bay, Cuba, will be tried.
However, Biden said he believes Mohammed will be found guilty regardless of the venue.
President Barack Obama will make the final decision about the trial, Biden said.
Republicans and some Democrats argue that terrorists should be treated not as criminals but as enemy combatants and tried by military commission.
"These policies are ill-conceived and they need to stop and start over," said Sen. Lindsey Graham, R-S.C.
Graham said he favors closing the jail at Guantanamo Bay because its existence helps recruit terrorists to al-Qaida. But he said that treating terrorists as criminals to be tried in civilian courts "is a huge mistake that will come back to haunt us."
Graham also said he thinks Obama should replace John Brennan, the president's counterterrorism adviser. Brennan on Saturday said that the rate of former Guantanamo inmates engaging in extremist or militant behavior - roughly one in five - "isn't that bad" compared to recidivism rates for U.S. prisoners of around 50 percent.
"Do you want someone in charge of counterterrorism who finds a 20 percent return-to-the-fight rate is acceptable? He has lost my confidence, and it's the best evidence yet how disconnected this administration has come from the fact that we're at war," Graham said.
Obama national security adviser James Jones, while not defending Brennan's statement, said Sunday the counterterrorism adviser does his job well and that the White House National Security Council is fortunate to have him.
Holder announced last year that Mohammed's trial would take place in federal court in New York City. City officials later opposed the idea because of costs, security and logistical concerns, and some senators are trying to stop any Guantanamo detainees from being brought to the United States for a civilian trial.
Jones said Holder is heading a review into the matter and will advise Obama on the course to take.
Biden appeared on NBC's "Meet the Press" and CBS' "Face the Nation." Jones appeared on "Fox News Sunday" and CNN's "State of the Union." Graham appeared on "Fox News Sunday."