The U.S. government called on Friday for the dismissal of a lawsuit brought by the Electronic Frontier Foundation against AT&T, arguing that evidence presented in the case could harm state secrets.

The invocation of the so-called "state secrets privilege" casts doubt on the outcome of the EFF's case, which alleges that AT&T inflicted harm on its American customers by cooperating with a comprehensive surveillance program conducted by the National Security Agency (NSA). The NSA's surveillance program first came to light in December. In January, the government was sued by the American Civil Liberties Union (ACLU) over the allegedly illegal and broad spying of ordinary American citizens, now thought to be broader spying than was originally reported.

The brief filed by the Assistant Attorney General and the U.S. Department of Justice argues that any evidence filed in the case could harm national security. It also cautions that the brief should not be seen as an admission that the allegations stated by the EFF's court filings are true.

"The fact that the United States will assert the state secrets privilege should not be construed as a confirmation or a denial of any of Plaintiff's allegations, either about AT&T or the alleged surveillance activities," the brief stated. "When allegations are made about purported classified government activities or relationships, regardless of whether those allegations are accurate, the existence or non-existence of the activity or relationship is potentially a state secret."

The U.S. plans to file a formal assertion of state secrets privilege, a motion to intervene in the case, and a motion to dismiss by May 12.