Washington: The White House insisted Thursday it must use every tool to protect Americans against terrorism, after revelations about a vast spy agency sweep of domestic phone records sparked a political backlash.
A civil liberties group branded the program, authorized by a top secret court order, as "beyond Orwellian" but a top Republican lawmaker said it had directly thwarted a terror attack in the United States in recent years.
The controversy looked set to widen as the Washington Post and Britain's Guardian newspaper reported that the National Security Agency (NSA) had tapped directly into the servers of Internet giants -- including Microsoft, Google, Facebook and Apple -- to obtain videos, photographs and emails.
The phone records program, which began under president George W. Bush, was detailed in a Guardian newspaper report Wednesday based on a copy of a secret court order requiring telephone provider Verizon to turn over call records.
Advocates say the data, collected on calls inside and outside the United States by the NSA, can be crunched to show patterns of communication to alert spy agencies to possible planning for terror attacks.
Senior US officials, while not confirming reports in the Guardian, defended the concept of collecting millions of phone records, and argued the program was lawful and subject to multiple checks and balances across the government.
"The top priority of the president of the United States is the national security of the United States. We need to make sure we have the tools we need to confront the threat posed by terrorists," White House spokesman Josh Earnest said.
"What we need to do is balance that priority with the need to protect civil liberties," he said, adding that President Barack Obama welcomed public debate on the issue.
Mike Rogers, Republican chairman of the House Permanent Select Committee on Intelligence, said the program was vitally important.
"Within the last few years this program was used to stop a terrorist attack in the United States. We know that," Rogers said.
Officials said the program did not "listen in" on calls or pull the names of those on the line, but simply collated phone numbers, the length of individual calls and other data.
A US official said the program allows counterterrorism investigators to find out whether suspected terrorists have been in contact with other suspects, particularly people located in the United States.
Randy Milch, Verizon's Executive Vice President and General Counsel, said in a message to staff he was legally forbidden to comment but that any such court order would compel the company to comply.
The revelations meant new controversy for the White House as it battles claims of harsh treatment toward leakers, accessing phone records of the Associated Press and targeting a Fox News reporter in an intelligence probe.
An NSA phone surveillance program was first reported during the Bush administration and formed part of sweeping anti-terror laws and a surveillance structure adopted after the September 11, 2001 attacks.
But the latest revelations are the first sign that the technique is continuing under Obama -- though laws authorizing such practices had already been reauthorized under the current president.
A top secret order by a court set up by the Foreign Intelligence Surveillance Act (FISA) issued on April 25 and obtained by the Guardian gives the US government unlimited power to collect data from a three month period ending on July 19.
It is unclear whether telephone providers other than Verizon have faced similar orders. In 2006, USA Today reported the NSA had collected phone records of tens of millions of Americans, using data provided by AT&T, Verizon and BellSouth.
"It's a program in which some untold number of innocent people have been put under the constant surveillance of government agents," said Jameel Jaffer, deputy legal director of the American Civil Liberties Union (ACLU).
"It is beyond Orwellian."
But Dianne Feinstein, chairwoman of the Senate Select Committee on Intelligence, said the program was lawful and couched in legal safeguards.
"The information goes into a database, the metadata, but cannot be accessed without what's called, and I quote, 'reasonable, articulable suspicion' that the records are relevant and related to terrorist activity," Feinstein said.
The Republican vice chairman of the committee, Saxby Chambliss, said the report showed nothing "particularly new" as the program was seven years old.
Another Republican, Senator Lindsey Graham, often a fierce Obama critic, also backed the program, saying: "If we don't do it, we're crazy."
"If you're not getting a call from a terrorist organization, you've got nothing to worry about," he said.