The Justice Department probably will never receive congressional approval to put the alleged Sept. 11 conspirators on trial in a civilian court, a key senator on the issue of terrorism trials said Sunday.

Sen. Lindsey Graham, R-S.C., said he believes he has the votes in the Senate to block alleged Sept. 11 mastermind Khalid Sheikh Mohammed from a civilian court.

Graham says the Sept. 11 suspect known as "KSM" and his alleged conspirators should be tried in military court at the U.S. naval base at Guantanamo Bay, Cuba. Civilian courts may be the right venue for some terrorism cases, Graham said, such as low-level al-Qaida operatives and the accused Christmas airliner bomber.

"I believe in all-of-the-above approach to terrorism trials," Graham said on "Fox News Sunday."

"I think it is a big mistake to criminalize the war, to take someone you've held under the law of war as an enemy combatant for six or seven years, then put them in civilian court. It is a disaster waiting to happen," he said.

Last year, Attorney General Eric Holder announced that Mohammed would be tried in federal civilian court in New York City, not far from the site of the destroyed World Trade Center. In the face of resistance from New York Mayor Michael Bloomberg and other local politicians, that plan was shelved and is now all but dead.

Raising security concerns, conservative Republicans staunchly oppose trials in civilian courts inside the United States for terrorism suspects, saying they should be tried instead before military commissions at Guantanamo Bay. The Obama administration says both civilian courts and military commissions should be available for such trials, pointing to the fact that dozens of terrorism-related cases have been handled in civilian courts.

Critics of the administration's approach also argue that trials in civilian courts run a greater risk of acquittals than in military courts because of rules of evidence and rights afforded to suspects.

The first Guantanamo Bay detainee to face a civilian trial, Ahmed Ghailani, was found guilty earlier this month of just one of the hundreds of charges brought against him in connection with attacks on two U.S. embassies in 1998. Although Ghailani faces up to life in prison for the single count, Republican lawmakers pointed to the case as a reason to support military trials for Guantanamo Bay detainees.

The case included some of the constitutional challenges that could arise in future trials. The judge barred the government from calling a key witness because the witness had been identified while Ghailani was being held at a secret CIA prison where harsh interrogation techniques were used.