Thank you London-based privacy watchdog, but we'll handle our own security.

By subjecting most visitors to scans of their faces and fingers, the United States will this week expand a mass surveillance system that threatens freedom and race relations.

London-based rights group Privacy International said in a report on Wednesday that the scheme relied on flawed technology and opaque, error-strewn watch lists on which innocent people could find themselves wrongly identified as security threats.

"There is no end to the uses to which this sensitive information will be put, nor any meaningful borders or boundaries limiting the flow of this data," it said.