The war in Iraq is "a major debacle," according to a study in the Pentagon's National Institute for Strategic Studies.

The report said that the United States has suffered serious political costs, with its standing in the world seriously diminished. Moreover, operations in Iraq have diverted "manpower, materiel and the attention of decision-makers" from "all other efforts in the war on terror" and severely strained the U.S. armed forces.

"Compounding all of these problems, our efforts there (in Iraq) were designed to enhance U.S. national security, but they have become, at least temporarily, an incubator for terrorism and have emboldened Iran to expand its influence throughout the Middle East," the report continued.

Read the report