Two Bulldogs stuffed with bombs and detonators were found by the US officers at Baghdad airport, The Sun reported.
The bombs had been primed to explode during the cargo aircraft's flight to Los Angeles.
But the dogs were never loaded on board as they had been killed by the lethal substances inside them.
The discovery, kept secret for two years, was revealed in France Friday, days after explosives were found inside printer cartridges last week.
One terrorism expert said: "It shows Al Qaeda militants' determination to wreak destruction by any means."