The strikes lit up the Baghdad sky

Last Friday's attacks sparked protests around the world, and inflamed UN-Iraqi relations, souring the atmosphere ahead of key talks aimed at paving the way for a lifting of the decade-old embargo on Iraq.

The revelations from the Pentagon come amid repeated US accusations that Chinese workers are in Baghdad - in breach of UN sanctions - installing fibre-optic cables to be used in Iraq's air defence.

China denied the allegation again on Thursday, saying it was to divert the outcry against the air strikes.

Weapon limitations

Stories that so-called "smart bombs" have gone off course are not new.

Last August, it emerged that the accuracy rate of bombs dropped by British forces during the 1999 Kosovo conflict was only 40%.

The strikes sparked protests around the world

Pentagon spokesman Rear Admiral Craig Quigley said the missiles fired at Iraq last week had achieved their purpose of "disrupting and degrading" radar systems near Baghdad.

But he also acknowledged the limitations of the strikes: "It isn't perfect. It never is."

Officials quoted by AP, however, say America's newest precision-guided bombs performed far worse than that, hitting fewer than 50% of targeted radars.

'New generation'

The RAF: "Content with success rate"

Analysts say the new bombs should be highly accurate because they rely on satellites rather than lasers, giving them an all-weather capability lacking in earlier versions of smart munitions.

Twenty-five individual aim points were targeted and the Pentagon can only confirm damage at eight of them.

One official, quoted in the Washington Post, said he had been told the bombs missed by an average of more than 100 yards (metres).

Checks are now being carried out to see if this might have been due to a software error.

Nonetheless, the Pentagon and the Royal Air Force insist that other weapons used against vital communications nodes or junctions were much more successful.

The RAF used older laser-guided bombs to hit a single target array and a Ministry of Defence spokesman in London told the BBC that they were "entirely content with their success rate".