The amount is likely to be conservative, reports say

KHAN BANI SAAD, Iraq - A $40 million prison sits in the desert north of Baghdad, empty. A $165 million children's hospital goes unused in the south. A $100 million waste water treatment system in Fallujah has cost three times more than projected, yet sewage still runs through the streets.

As the US draws down in Iraq, it is leaving behind hundreds of abandoned or incomplete projects. More than $5 billion in American taxpayer funds has been wasted - more than 10 percent of the some $50 billion the US has spent on reconstruction in Iraq, according to audits from a US watchdog agency.