A report published by the US Army War College has criticised the war against Iraq as a strategic error.
The report echoes the views of many opponents of the war
It also suggests that the Bush administration's global war on terror may be unsustainable.
The report, by academic Jeffrey Record, has been dismissed by US defence officials, who say it does not represent the view of the US Army.
But BBC Pentagon correspondent Nick Childs says the report could be an embarrassment for the Pentagon.
'War of choice'
The author of the report is a visiting professor at the prestigious college in Pennsylvania and his conclusions about the Bush administration's conduct of its war on terrorism appear quite damning.
He calls the invasion of Iraq "an unnecessary war of choice" and a "detour".
Mr Record says that by lumping together a host of threats - from the destruction of the al-Qaeda network to stopping the spread of weapons of mass destruction - the administration has set goals in the war which are unsustainable.
"The United States may be able to defeat al-Qaeda, but it cannot rid the world of terrorism, much less evil," he says in the report.
Mr Record adds: "[The war] against a deterred Iraq has created a new front in the Middle East for Islamic terrorism and diverted attention and resources away from the security of the American homeland against further assault by an undeterrable al-Qaeda."
US officials have played down the report. They say the views are those of the author alone and do not represent any official policy.
In a disclaimer, the US Army's War College's Institute for Strategic Studies adds that the report does not represent the views of the college.
They said staff and students at the War College are encouraged to be critical and that the college was founded to promote independent analysis.
Our correspondent says the suspicion will nevertheless be that the views are shared by some in the US Army.
Mr Record's views also echo many of the criticisms made by the administration's political opponents.