Ridge told BBC's Newsnight programme that the US administration had stepped up security after "a stream of intelligence" pointed to an air attack on cities in the United States.

"It talks about attacks equal to or greater than those that occurred on September 11, talked about these attacks occurring in a time frame that covered our traditional holiday period, and it also included reference to aviation," Ridge said.

Ridge told the BBC that the intelligence pointed to specific flights which the British, French and Mexican governments "are very much aware of, as are the travelling public in those countries."

"Some of (the intelligence) is a direct result of analysis from multiple sources and some of it is from very specific sources that have given us some specific information the nature of which we viewed as credible and we've been able in some measure to corroborate," Ridge said.

Ridge, speaking after talks with British government officials in Washington over improving airline security, said both countries wanted to draw up guidelines on how to respond to terror threats.

The talks came as British Airways flight 223 from Heathrow to Washington was delayed Wednesday for the fifth successive day after US authorities demanded more information on the passengers making the trip.