* GOP accuses White House of attempt to "civilianize" war
* Obama aides say FBI, Justice inquiries could be damaged
* One suspect held by military had suite of cells
WASHINGTON, Nov 23 (Reuters) - A Senate plan requiring that all foreign al Qaeda suspects found in the United States be turned over to the military instead of civilian law enforcement could gravely damage U.S. counter-terrorism investigations, the Obama administration warned.
Top administration officials charged that the plan would set up new hurdles for U.S. investigators - particularly at the FBI and the Justice Department - and would raise questions as to how and when they must involve the military.
Democrats and Republicans on the Senate Armed Services Committee, in a rare display of bipartisanship, approved the provision earlier this month as part of an important defense bill. It could be voted on by the full Senate early next week.
Officials said that if the current plan is approved by both the House and Senate, Obama aides will recommend a presidential veto of the entire defense bill, which contains many other vital defense-related provisions.
"Agents and prosecutors should not have to spend their time worrying about citizenship status and whether and how to get a waiver signed by the Secretary of Defense in order to thwart an al Qaeda plot against the homeland," Lisa Monaco, assistant attorney general for national security, told Reuters.
"Rather than provide new tools and flexibility for FBI operators and our intelligence professionals, this legislation creates new procedures and paperwork for FBI agents, intelligence lawyers and counter-terrorism prosecutors," she said.
Currently, suspects detained in the United States normally go into the civilian justice system, while those caught overseas are held under U.S. military jurisdiction.
The dispute appears to be about more than just bureaucratic turf battles, and risks reopening bitter disputes over handling militant suspects that in some cases have taken a decade to resolve.
NO 'MIRANDA' REQUIRED
One prominent Republican backer of the plan, Senator Lindsay Graham, said that in his view, the Obama administration has been too eager to process al Qaeda suspects caught in the United States through the civilian criminal justice system.
This usually involves them quickly being given the mandatory "Miranda" warnings about their rights to legal counsel and to remain silent, he said.
Requiring that the administration transfer foreign al Qaeda suspects into military custody, Graham said in an interview on Wednesday, would give investigators time to interrogate suspects and gather intelligence about potential plots without giving them warnings which might cause them to stop talking.
"Military custody is the best place for intelligence gathering," Graham said, adding that Congress was "fed up" with administration moves to "civilianize" what some legislators still regard principally as a war against militants.
A congressional aide close to backers of the committee plan insisted that it gives the administration the freedom to make a determination on military custody.
"If the FBI is investigating, they investigate. No ongoing surveillance, intelligence gathering or interrogation is interrupted" under the bill's provisions, the aide insisted.
Under the plan, unanimously approved by the committee, military custody requirements would apply both to suspects detained by U.S. forces overseas, and to suspects alleged to be connected to al Qaeda or an "associated force" of foreign nationality who are detained on U.S. soil.
Al Qaeda suspects of U.S. nationality or residency arrested in the United States. would still be processed through the civilian court system.
After complaints from the White House, the Armed Services Committee tweaked its proposal to include a provision authorizing the administration to formally waive the military custody provisions in cases where it deems that national security would benefit from such a move.
As an example of how military handling of detainees is not an intelligence-producing panacea, law enforcement officials cited the case of an alleged al Qaeda "sleeper agent" of Saudi and Qatari nationality who was picked up in the United States after the attacks of September 11, 2001.
According to the officials, Ali al-Marri was initially arrested as a material witness, then charged in civilian courts with credit card and identity fraud violations. But in 2003, President George W. Bush designated al-Marri as an "enemy combatant" and had him transferred to a military brig in South Carolina.
Instead of being treated harshly, U.S. officials said, al Marri was given a suite of cells at the military prison, complete with his own Islamic library and exercise equipment. Despite repeated questioning by military interrogators over several years, the officials said, al Marri never provided them with any information.
However, the officials said, after President Obama in 2009 ordered that al Marri's case be reviewed, he was subsequently transferred back into the civilian court system.
He eventually pleaded guilty to a conspiracy charge in which he admitted dealings with alleged top al Qaeda operative Khalid Sheikh Mohammed and his involvement in alleged research into chemical weapons on al Qaeda's behalf. However, he did not give prosecutors or civilian investigators additional information.