WASHINGTON — The Supreme Court has rejected a challenge to the Bush administration's domestic-spying program.

The justices' decision today includes no comment explaining why they were turning down the appeal from the American Civil Liberties Union.

The ACLU wanted the Court to allow a lawsuit by the group and individuals over the National Security Agency’s warrantless wiretapping. Last July, a 6th U.S. Circuit Court of Appeals panel ruled 2-1 to dismiss the lawsuit because the plaintiffs couldn’t prove whether their communications had been monitored.

The government has refused to turn over information about the closely guarded program that could reveal who has been under surveillance.

Steven R. Shapiro, the ACLU’s legal director, has said his group is in a "Catch-22" because the government says the identities of people whose communications have been intercepted is secret. But only people who know they have been wiretapped can sue over the program, Shapiro has said.

The 9th Circuit last year ruled against an Islamic charity that also challenged the program, concluding that a key piece of evidence was protected as a state secret.

In that case, the Oregon-based U.S. arm of the Al-Haramain Islamic Foundation alleged the NSA illegally listened to its calls. The charity had wanted to introduce as evidence a top-secret call log it received mistakenly from the Treasury Department.

A separate lawsuit against telecommunications companies that have cooperated with the government is pending in the San Francisco-based appeals court. A federal judge is also examining whether the warrantless surveillance of people in the United States violates the law that regulates the wiretapping of suspected terrorists and requires the approval of a secret court.

The case the Court acted on today is ACLU v. NSA, 07-468.