Updated

Three federal appeals judges are stepping into a debate over privacy rights and government surveillance, weighing whether the National Security Agency's phone data collection program is constitutional.

The Justice Department will tell the Republican-appointed appeals judges on Tuesday that collecting the phone data is of overriding and compelling importance to the nation's security.

The government is using a 35-year-old Supreme Court ruling on phone surveillance as the legal underpinning for gathering the phone data of millions of Americans.

In challenging the program, opponents are invoking a recent Supreme Court opinion restricting warrantless cellphone searches.

The three judges have generally come down on the government's side on national security issues.

Former NSA systems analyst Edward Snowden revealed the phone data collection effort a year and a half ago.