A government programme that included the collection of telephone records thwarted at least one significant terrorist attack in the United States, the chairman of the US House of Representatives Intelligence Committee has said.
Representative Mike Rogers, a Michigan Republican, spoke out on Thursday after the White House was forced to defend a court order allowing the government to secretly collect millions of US citizens' telephone records, calling it a critical tool to fight security threats.
"Within the last few years, this programme was used to stop a terrorist attack in the United States. We know that,"
Rogers told a news conference.
"It was a significant case."
Rogers declined to provide details, but said politicians were trying to get enough information about the thwarted attack declassified to share the information with the public.
He stressed that the telephone records programme was legal, authorised by Congress and supervised by a court.
British newspaper The Guardian published on Wednesday a secret court order related to the collection of records of millions of customers of Verizon Communications.
White House spokesman Josh Earnest defended the actions.
He said he could not discuss classified information, but the court order in question allowed the intelligence community to know when terrorists or suspected terrorists were engaged in dangerous activities.
Earnest said the order did not allow the government to listen in on calls and only included details like telephone numbers.
He said there was a robust legal regime overseeing the programme and that Congress has been fully briefed.
The Guardian reported that the National Security Agency was collecting the telephone records of millions of US customers of Verizon under a top secret court order, later confirmed by Democratic senator Dianne Feinstein.
The order was granted by the secret Foreign Intelligence Surveillance Court on April 25 and was good until July 19.
'Ongoing, daily basis'
The order requires Verizon, one of the nation's largest telecommunications companies, on an "ongoing, daily basis" to give the NSA information on all telephone calls in its systems, both within the US and between the US and other countries.
The Guardian said the document, a copy of which it had obtained, shows for the first time that under the Obama administration the communication records of millions of US citizens were being collected indiscriminately and in bulk, regardless of whether they were suspected of any wrongdoing.
Under the terms of the order, the phone numbers of both parties on a call are handed over, as is location data, call duration, unique identifiers, and the time and duration of all calls.
The contents of the conversation itself are not covered, The Guardian said.
The broad, unlimited nature of the records being handed over to the NSA is unusual. FISA court orders typically direct the production of records pertaining to a specific named target suspected of being an agent of a terrorist group or foreign state, or a finite set of individually named targets. NSA warrantless wiretapping during the George W Bush administration after the 9/11 attacks was very controversial.
The FISA court order, signed by Judge Roger Vinson, compelled Verizon to produce to the NSA electronic copies of "all call detail records or telephony metadata created by Verizon for communications between the United States and abroad" or "wholly within the United States, including local telephone calls", The Guardian said.
The law on which the order explicitly relies is the "business records" provision of the USA Patriot Act.