President Barack Obama’s administration on Thursday defended a newly disclosed National Security Agency program that gathers telephone records of tens of millions of Verizon customers, authorized under a secret court order.

In an unusual move, James Clapper, director of national intelligence, responded to a newspaper report about the program by declassifying certain aspects of the law to explain to the public the limitations of the program. He said it could only be used if there is “a reasonable suspicion” of a connection with a foreign terrorist organization.

“The highest priority of the intelligence community is to work within the constraints of law to collect, analyze and understand information related to potential threats to our national security,” he said in a statement late Thursday.

On Capitol Hill, key lawmakers from both parties said they have known about the program for years, while others said they were never informed of the scope of the collection, which appeared to impact Americans not suspected of any wrongdoing.

“It was like, oh God, not one more thing,” Sen. Barbara Mikulski, D-Md., told Attorney General Eric Holder during an unrelated Appropriations Committee meeting. “And not one more thing where we’re trying to protect America, and then it looks like we’re spying on America.”

The program, first reported Wednesday by the Guardian newspaper in London, requires Verizon to provide the NSA, an intelligence agency within the Department of Defense, with daily information on calls by its customers both in the United States and from foreign locations into the United States. The information includes numbers dialed and received and lengths of calls, but not the content of the calls.

A former senior NSA official said the database is more valuable than the content of communications because it allows the NSA to construct “maps” of an individual’s daily movements, social connections, travel habits and other personal information.