The Senate Armed Services Committee on Tuesday modified provisions governing the detention of terrorism suspects that had drawn a veto threat from the White House, but the administration and leading Democrats said the new language in a defense spending bill failed to address their concerns.

The new provisions of the National Defense Authorization Act were crafted in a deal between the Democratic chairman of the committee, Sen. Carl M. Levin (Mich.), and the ranking Republican, Sen. John McCain (Ariz.). The senators issued a statement saying the new measure was “an effort to address concerns raised by the administration and others.”

The administration had complained that the detainee provisions would require the military to take custody of any member of al-Qaeda, or anyone involved in planning an attack, even if they are captured in the United States. The administration said the provisions could force federal law enforcement agencies to turn over suspects to the military, potentially disrupting interrogations and investigations.

Levin insisted that the new language will not interfere with any law enforcement operations and that the administration will have discretion about whom to detain and how.

“If there’s an al-Qaeda guy here attacking the military base. Some guy walks up to a military base and blows himself up . . . can that person be detained by the military at that fort?” Levin told reporters. “Under the administration language you could not mandate that. We say, yeah, you can mandate that, and if you don’t like it, administration, you can waive that.”

Defense Secretary Leon E. Panetta, in a letter to Levin on Tuesday, said part of the bill still “restrains the Executive Branch’s options to utilize, in a swift and flexible fashion, all the counterterrorism tools that are now legally available.”

Some leading Democrats also remain opposed to the measure.

“I continue to have grave concerns about the detainee provision . . . not the least of which is that questions remain about the impact on American citizens and counterterrorism operations,” said Sen. Mark Udall (Colo.), a member of the Armed Services Committee. “I do not believe that the consequences of the provisions have been adequately considered.”

Human rights and civil liberties groups said the authority to detain has gotten broader when they had wanted it narrowed. And they said the bill could now be interpreted to allow the president to detain indefinitely without charge or trial an American citizen picked up in the United States in a terrorism investigation.

“With Osama bin Laden dead and the military pulling out of Iraq and downscaling its role in Afghanistan, there is absolutely no reason for Congress to now pass legislation that would put in indefinite military detention American citizens and other suspects apprehended far from any battlefield, even within the United States itself,” said Christopher Anders, senior legislative counsel for the American Civil Liberties Union.

The measure would also extend for another year restrictions on the transfer of detainees out of the U.S. military prison at Guantanamo Bay, Cuba, for repatriation or resettlement in third countries.