The United States this year will have spent [at least] $100 billion on contractors in Iraq since the invasion in 2003, a milestone that reflects the Bush administration's unprecedented level of dependence on private firms for help in the war, according to a government report to be released [on August 12]. The report, by the Congressional Budget Office ... will say that one out of every five dollars spent on the war in Iraq has gone to contractors for the United States military and other government agencies. The Pentagon's reliance on outside contractors in Iraq is proportionately far larger than in any previous conflict, and it has fueled charges that this outsourcing has led to overbilling, fraud and shoddy and unsafe work that has endangered and even killed American troops. The role of armed security contractors has also raised new legal and political questions about whether the United States has become too dependent on private armed forces on the 21st-century battlefield. The budget office's report found that from 2003 to 2007, the government awarded contracts in Iraq worth about $85 billion, and that the administration was now awarding contracts at a rate of $15 billion to $20 billion a year. At that pace, contracting costs will surge past the $100 billion mark before the end of the year. Through 2007, spending on outside contractors accounted for 20 percent of the total costs of the war, the budget office found. The dependence on private companies to support the war effort has led to questions about whether political favoritism has played a role in the awarding of multibillion-dollar contracts.