The FBI said innocent people had nothing to fear from a database

The FBI is due to award a $1bn (£0.5bn) contract next month for the databank of peoples' physical characteristics.

FBI assistant director Thomas E Bush told the BBC the targets would be what he called the "bad guys" - terrorist and criminal suspects.

But civil liberties groups have warned the technology may be unreliable.

The FBI system is expected to contain a range of biometric information, including eventually iris images and face-shape data.

'Careful vetting'

Mr Bush told the BBC that innocent people would have nothing to fear from the database, called Next Generation Identification.

"Post-9/11 we've had an increase in our customer base. We need a system that is literally bigger, faster better," he said.

"What we deal with is bad guys data, suspected terrorists or criminals."

He added that there would be "very careful vetting" to ensure that the system is not abused.

However Barry Steinhardt of the American Civil Liberties Union told the Washington Post that it would enable an "always-on surveillance society".

The newspaper says the FBI, which already has 55m sets of digital fingerprints, has also been compiling images of faces and palm patterns.