AUSTRALIA secretly worked with the United States to weaken a key international treaty to ban cluster bombs, according to leaked US diplomatic cables.

Despite taking a high-profile stance against cluster munitions - condemned as the cause of large numbers of civilian casualties - Australia was privately prepared to pull out of international negotiations for a global ban of the weapons if this threatened ties with US forces.

The US continues to claim cluster munitions are ''a legitimate and useful weapon'', including for use in Afghanistan, and has affirmed that it will not sign the treaty to ban the bombs.

The disclosure comes as Federal Parliament prepares to consider a bill to ratify Australia's signature of the cluster munitions convention.

The draft legislation has attracted sharp criticism from non-government organisations for not meeting the spirit of the treaty to ban the weapons.