Citing national security concerns, the U.S. Department of Justice has sued the New Jersey Attorney General's office to prevent it from asking telephone companies whether they gave customer call records to the National Security Agency, reports Reuters. The suit was filed in Trenton, NJ, on Wednesday, one day before the phone companies - AT&T, Verizon, Cingular, Sprint Nextel and Qwest - were supposed to reply to subpoenas, issued by AG Zulima Farber.

"Compliance with the subpoenas issued by those officers would first place the carriers in a position of having to confirm or deny the existence of information that cannot be confirmed or denied without causing exceptionally grave harm to national security," the lawsuit said.

David Wald, a spokesperson for the New Jersey AG, said the office had "acted to determine whether the rights of citizens in New Jersey have been violated. We will look at this complaint (by the Justice Dept.) and respond in court."