“We should not be increasing the danger of another terrorist strike against Americans at home and abroad,” said Representative Peter T. King, Republican of New York.

Senator Jim Webb, Democrat of Virginia, questioned the wisdom of trying terrorism suspects in civilian courts, arguing that military commissions were more appropriate. But many other Democrats praised the move, noting that New York had been the setting for other high-profile terrorism trials  including the prosecution of Omar Abdel Rahman, the “blind sheik” who was convicted of plotting to blow up the United Nations headquarters and other New York landmarks.

“New York is not afraid of terrorists,” said Representative Jerrold Nadler, Democrat of New York, adding, “Any suggestion that our prosecutors and our law enforcement personnel are not up to the task of safely holding and successfully prosecuting terrorists on American soil is insulting and untrue.”

Image A photograph taken by the International Committee of the Red Cross of Khalid Shaikh Mohammed this year in Guantánamo Bay, Cuba. The detainee's family released the photo to a Web site, www.muslm.net. Credit... Associated Press

Mr. Holder said he was confident that the men would be convicted, and other administration officials said they had ample legal authority to keep classified information secret. They also suggested that they could continue to detain anyone deemed to be a “combatant” under Congress’s authorization to use military force against Al Qaeda.

Mr. Mohammed and the other detainees would not be moved right away. Under a recently enacted law, the administration must give Congress 45 days notice before bringing any Guantánamo Bay detainee into the United States. Mr. Holder said the administration would comply with that requirement as it seeks indictments from a grand jury.

The decision to prosecute some detainees in civilian court was a major policy shift from the Bush administration, which contended that suspected Al Qaeda members should not be treated like  nor given the rights of  ordinary criminals. It had charged the Sept. 11 defendants before a military commission at Guantánamo, which has a more flexible standard for evidence.