In a 50-page memorandum filed in US district court, southern district of New York on behalf of the US government, the lawyers including India-born Manhattan Attorney Preet Bharara said the court should grant summary judgment and dismiss the complaints as the information about the drone strikes is "classified."
The New York Times and rights group American Civil Liberties Union had, through a Freedom of Information Act, sought records relating to the US government's "use of targeted lethal force against US citizens and other persons associated with the Al- Qaeda and other terrorist groups."
One instance of information requested through the lawsuit is about drone operations that led to the death of US-born cleric Anwar al-Aulaki.
The ACLU also wants information about how the government got the evidence that led the administration to kill three Americans, including a 16-year-old boy, last year.
"Whether or not the CIA has the authority to be, or is in fact, directly involved in targeted lethal operations remains classified. And that is so notwithstanding the unsourced, unofficial statements and media reports that plaintiffs have identified.
"None of those statements or reports constitutes an official disclosure that could vitiate agencies' ability to safeguard the classified and other statutorily protected information at issue here, and none eliminates the national security harms that could result from disclosure of such information," the government said.
The brief was filed by the Obama administration shortly before a midnight deadline on Wednesday.
The ACLU condemned the move by the US government to defend the secrecy surrounding the "targeted killing" programme.
"The notion that the CIA's targeted killing programme is still a secret is beyond absurd. Senior officials have discussed it, both on the record and off. They have taken credit for its putative successes, professed it to be legal, and dismissed concerns about civilian casualties," ACLU Deputy Legal Director Jameel Jaffer said.
Jaffer said if the government can make "claims" about the drone strikes to the media, it can answer requests under the Freedom of Information Act.
"The public is entitled to know more about the legal authority the administration is claiming and the way that the administration is using it. The administration should release the legal memos that purportedly justify the targeted killing programme, and it should release more information about the process by which individuals, including American citizens, are added to government kill lists," Jaffer said.
The ACLU said it has "profound concerns" with the power the administration is claiming and with the proposition that the president should be permitted to exercise this power without oversight by the courts.
"That the administration believes a power so sweeping should be exercised in secret is astounding," it said.
The government said it has taken steps like speeches by top officials, including President Barack Obama's chief counterterrorism adviser John Brennan, that have "set forth for the American people the legal analysis and process involved in the determination whether to use lethal force."
