• Records legally obtained without a judge's approval or grand jury subpoena

• It is unusual for Pentagon, CIA to investigate domestic cases

• Move called part of a post-9/11 strategy to be aggressive in intelligence-gathering

WASHINGTON (AP) -- The Pentagon and to a lesser extent the CIA have been using a little-known power to look at the banking and credit records of hundreds of Americans and others suspected of terrorism or espionage within the United States, according to a published report.

"It is our understanding that the intelligence community agencies make such requests on a limited basis," said Carl Kropf, a spokesman for the Office of the National Intelligence Director, which oversees all 16 spy agencies in the government.

The so-called national security letters permit the executive branch to seek records about people in terror and spy investigations without a judge's approval or grand jury subpoena. Government lawyers maintain the legal authority for such tactics is years old and was strengthened by the Patriot Act.

The Federal Bureau of Investigation, the lead agency on domestic counterterrorism and espionage, has issued thousands of national security letters since the attacks of September 11, 2001.

That has prompted criticism and court challenges from civil liberties advocates who claim they invade the privacy of Americans' lives, even though banks and other financial institutions typically turn over the financial records voluntarily.

The New York Times, in an article posted Saturday on the Internet, said the Pentagon and CIA also have been using their own versions of the letters to aid investigative work.

Congressional officials said members of the House and Senate Intelligence Committees had been briefed on the Pentagon and CIA's use of the letters, the newspaper said.

The vast majority of national security letters are issued by the FBI, but in very rare circumstances they have been used by the CIA before and after 9/11, said a U.S. intelligence official who spoke to The Associated Press on condition of anonymity because of the issue's sensitivity.

The CIA has used these non-compulsory letters in espionage investigations and other circumstances, the official said.

"It is very uncommon for the agency to be issuing these letters," the official said. "The agency has the authority to do so, and it is absolutely lawful."

A government official, also speaking on condition of anonymity, said one example of a case in which the letters were used was the 1994 case of CIA officer Aldrich Ames, who eventually was found to have been selling secrets to the Soviet Union.

Neither official commented about the extent of possible use by Defense Department agencies, but Pentagon officials defended their use to the Times, saying they were part of a post-September 11 strategy to use more aggressive intelligence-gathering techniques.

Kropf's remarks to the AP did not address specifics of the Times story, which said military intelligence officers have sent letters in up to 500 investigations.

"There's a strong tradition of not using our military for domestic law enforcement," said Elizabeth Rindskopf Parker, a former general counsel at both the National Security Agency and the CIA and dean at the McGeorge School of Law at the University of the Pacific told the Times. "They're moving into territory where historically they have not been authorized or presumed to be operating." LINK__CNN