Coming soon to TV news everywhere: We must invade the next country because we've worn out out welcome in the last one.

The Bush administration focused on alleged weapons of mass destruction as the primary justification for toppling Saddam Hussein by force because it was politically convenient, a top-level official at the Pentagon has acknowledged.

The extraordinary admission comes in an interview with Paul Wolfowitz, the Deputy Defence Secretary, in the July issue of the magazine Vanity Fair.

Mr Wolfowitz also discloses that there was one justification that was "almost unnoticed but huge". That was the prospect of the United States being able to withdraw all of its forces from Saudi Arabia once the threat of Saddam had been removed. Since the taking of Baghdad, Washington has said that it is taking its troops out of the kingdom. "Just lifting that burden from the Saudis is itself going to the door" towards making progress elsewhere in achieving Middle East peace, Mr Wolfowitz said. The presence of the US military in Saudi Arabia has been one of the main grievances of al-Qa'ida and other terrorist groups.