US: Senators today start hearings into the legality of President Bush's decision to allow the National Security Agency (NSA) to eavesdrop on American citizens' international phone calls without a warrant.
Democrats on the Senate judiciary committee are expected to subject US attorney general Alberto Gonzales to sharp questioning about the programme, which some legal experts say is illegal, at a public hearing today. On Thursday, Mr Gonzales will appear at a closed-door session of the Senate intelligence committee with Michael Hayden, deputy director of national intelligence.
The Bush administration, which claims that the president's war powers allowed him to authorise the spying programme, has refused to hand over any documents relating to it.
Democrats say a 2001 congressional resolution authorising "necessary and appropriate" military force against those who planned or perpetrated the 9/11 terrorist attacks did not authorise the surveillance. They also argue that the programme violates a 1978 statute, known as the Foreign Intelligence Surveillance Act (FISA).
The administration argues that Congress has no authority to circumscribe Mr Bush's constitutional role as commander in chief and that the gathering of signals intelligence is integral to war fighting and thus within the powers of the president.
The Washington Post reported yesterday that as many as 5,000 Americans may have had their international phone calls intercepted under the programme but that only a handful were deemed to have had any contact with terrorists.
Fewer than 10 US citizens or residents a year, the paper said, have aroused enough suspicion during the warrantless eavesdropping to justify interception of their domestic calls, which requires a warrant from a federal judge.
Citing "current and former government officials and private sector sources with knowledge of the technologies in use", the paper said that the NSA surveillance takes place in several stages, the earliest by machine.
Computer-controlled systems collect and sift basic information about hundreds of thousands of faxes, e-mails and phone calls before selecting some for human scrutiny.
This week's Senate hearings could cast light on some features of the surveillance programme that remain unknown, such as what happens to non-threatening e-mails and conversations the NSA intercepts.
The ranking Democrat on the intelligence committee, West Virginia's John D Rockefeller, has said the administration's limited briefings to legislators have been insufficient and prevented Congress from exercising its constitutional oversight responsibility.
Mr Rockefeller wants senators to be able to question administration witnesses on operational details, such as the number of Americans targeted for surveillance and the programme's effectiveness in preventing terrorist attacks.