A group that advocates privacy rights said on Wednesday it planned to sue the Justice Department to win the public release of documents related to President George W. Bush"s domestic eavesdropping program.

The Electronic Privacy Information Center, or EPIC, is the latest of a number of civil liberties organizations to take the federal government to court over the domestic spying program, which has caused an outcry among Republicans and Democrats alike.

The American Civil Liberties Union and the Center for Constitutional Rights filed separate lawsuits on Tuesday, challenging the highly classified program that allows the National Security Agency to monitor U.S. citizens" international telephone and e-mail messages without first obtaining warrants.

EPIC said it would ask a federal district court in Washington on Thursday to order the release of related Justice Department documents that the government has failed to disclose under the Freedom of Information Act.

The 1966 FOIA law sets out procedures that allow the public to request the release of government documents and records.

EPIC submitted FOIA requests with four Justice Department offices including the Office of the Attorney General after the New York Times first reported the existence of the warrantless surveillance program on December 16.

The Justice Department said it responded quickly to EPIC"s requests by agreeing to expedite the FOIA process. "The department continues to work in an expedited manner to meet this request," Justice spokesman Brian Roehrkasse said.

The Washington-based group contends that the Justice Department has played a key role in authorizing, implementing and overseeing the NSA program.

"The Administration has confirmed the existence of the program, but released very little information that sheds light on the key question (of) whether the government is acting illegally," EPIC general counsel David Sobel said in a statement.

The 1978 Foreign Intelligence Surveillance Act makes it illegal for the U.S. government to spy on Americans in the United States without first getting approval from a secret federal court.

The program"s existence has been acknowledged by Bush and defended by Attorney General Alberto Gonzales, who is scheduled to appear at a February 6 hearing on the program before the Senate Judiciary Committee.

Records sought by EPIC include an audit of the NSA program, a "checklist" guide used to determine whether an individual"s phone or e-mail messages could be monitored, documents showing how information gleaned through eavesdropping had been used, and other legal opinions about the program.