WASHINGTON (AP) — Government lawyers are asking a federal judge to issue a stay temporarily preventing further proceedings in a lawsuit that threatens a National Security Agency surveillance program targeting the calling records of millions of American phone users.

Justice Department lawyers asked U.S. District Judge Richard Leon late Wednesday to halt further proceedings in the lawsuit in his court until the U.S. Court of Appeals for the District of Columbia Circuit hears an appeal of Leon’s recent ruling in a challenge to the government’s data collection program. In December, Leon questioned the constitutionality of the surveillance program in a decision that, if upheld, could torpedo the operation.