US officials say the operation to remove military hardware and vehicles from Afghanistan as troops withdraw after 12 years of war will cost between $US5 billion and $US6 billion.
Statistics released by the military about the process known as a "retrograde" show 25,000 vehicles have been shipped out of Afghanistan in the past year and another 25,000 are still to go.
About 100,000 containers ill be used to remove mountains of equipment ranging from fighting gear to fitness machines, furniture and computers, AFP reports.
Brigadier-General Steven Shapiro said the retrograde from Afghanistan is "one of the most challenging military transportation operations in history in terms of scale and complexity."
Most of the hardware will be flown out of land-locked Afghanistan or taken by road to the Pakistani port of Karachi, though the route has been hit by militant attacks and was temporarily closed by spats between Washington and Islamabad.
