Haunted by the failure to capture Osama bin Laden in Afghanistan, Washington is putting in place plans to limit the damage if it fails to topple the Iraqi leader swiftly.

They rest in part on persuading the Iraqi people that US forces control the country even before Saddam’s demise. The Pentagon is planning to drop emergency food and medical aid from the first day of airstrikes to try to win the “hearts and minds” of locals so that they will support the ensuing invasion.

The opening days of the war are planned as a massive air assault aimed at collapsing Saddam’s command structure, followed by a “rush for Baghdad” by ground forces. US special forces and CIA teams are already operating on the ground in Iraq. But if US forces cannot find Saddam or present credible evidence that he is dead, they will face stiffer resistance from the Iraqis. “If people think Saddam is still alive they will be frightened to come out and support us, even if he is powerless,” one US official said.

The American failure to get bin Laden “dead or alive”, in Mr Bush’s words, has provided an unsettling background to war planning in Iraq. “Osama bin Laden hangs very heavy over Iraq,” the official said. “We can’t afford another repeat.”

There are formidable difficulties in finding Saddam, who has numerous body doubles and rarely sleeps in the same place two nights running, and America is hoping that its massive show of force will prompt a “palace revolt”.