Two top senators urged the Obama administration on Monday to transfer the suspect in the failed Christmas Day airline bombing to the Pentagon, blasting the Justice Department for reading him his Miranda rights and treating him like a common criminal.

Citing reports that Umar Farouk Abdulmutallab was "speaking openly about the attack" and Al Qaeda in the Arabian Peninsula's involvement in it before he was read his Miranda rights, Sens. Joe Lieberman and Susan Collins said that reading the suspect his rights shortly after his arrest was an opportunity lost. 

Lieberman, I-Conn., chairman of the Senate Homeland Security and Governmental Affairs Committee, and Collins, R-Maine, the committee's ranking Republican, said officials would be able to continue interrogating Abdulmutallab and try him before a military commission if they treat him as an enemy combatant.

"The decision to treat Abdulmutallab as a criminal rather than (an unprivileged enemy belligerent) almost certainly prevented the military and the intelligence community from obtaining information that would have been critical to learning more about how our enemy operates and to preventing future attacks," the senators wrote in a letter to Attorney General Eric Holder and counterterrorism adviser John Brennan

"Though the president has said repeatedly that we are at war, it does not appear to us that the president's words are reflected in the actions of some in the executive branch, including some at the Department of Justice," they wrote. 

Sen. Jeff Sessions, R-Ala., also released a written statement Monday urging Obama to revoke Abdulmutallab's "civilian status," saying the administration "squandered an invaluable opportunity to gather intelligence from a captured terrorist fresh from Al Qaeda's operation in Yemen." 

Though Abdulmutallab has already been indicted in anticipation of a civilian trial, attorney Edward MacMahon said there is precedent for treating suspects as enemy combatants before trying them in civilian court. 

MacMahon, former attorney for Al Qaeda conspirator Zacarias Moussaoui, said the administration would be in its right to treat Abdulmutallab as an enemy combatant and interrogate him, despite the case that is already underway. He said the administration would not have to worry about jeopardizing his confession, since there's enough physical evidence and witness testimony to convict him. 

The calls for the Justice Department to do an about-face on Abdulmutallab's civilian trial come after new questions were raised during congressional hearings last week about the way the suspect was handled after the attempted bombing. 

In one hearing, Director of National Intelligence Dennis Blair said Abdulmutallab should have been questioned by the recently created High-Value Detainee Interrogation Group, or HIG. But he later released a statement noting that the HIG is not yet "fully operational." 

Still, key officials -- among them FBI Director Robert Mueller -- have said they were not consulted on the decision to treat Abdulmutallab as a civilian. 

Fox News has confirmed that local FBI agents interviewed the suspect for about 50 minutes after he was taken to the University of Michigan Medical Center. One official said he spoke freely during this period and claimed to be a trained recruit for Al Qaeda in the Arabian Peninsula. 

After that, he went into surgery. He was then advised of his right to remain silent, and he subsequently obtained a lawyer. 

Lieberman and Collins wrote Monday that the "unilateral decision" by the Justice Department to treat the suspect as a criminal "and to forego information that may have been extremely helpful to winning this war demonstrates" that some in the department are not acting as if the country is at war. 

"The administration can reverse this error, at least to some degree, by immediately transferring Abdulmutallab to the Department of Defense," they wrote. 

Fox News' Catherine Herridge contributed to this report.