The report is particularly critical of the policies and tactics pursued by Kurdish authorities who control Nineveh’s disputed territories through the heavy presence of their security forces and political party offices. The report describes how the Kurdish government has sought to repress minorities, subsume the identity of Shabaks and Yazidis into that of Kurds and sow rifts within the groups with bribes and patronage while suppressing dissent through violence, torture, arrests and killings.

The United States military has recognized the Arab-Kurdish conflict in northern Iraq as the main driver for continued instability in Iraq. The disputed territories extend from Sinjar in Nineveh, in northwestern Iraq, to Mandali in Diyala Province, in the east, and include the oil-rich city of Kirkuk.

After a series of bombings in July and August against minorities in Nineveh that killed at least 143, wounded scores and flattened villages, the American military commander in Iraq, Gen. Ray Odierno, announced plans to deploy United States troops along with members of the Kurdish pesh merga force and the Iraqi Army in the disputed areas to stop groups linked to Al Qaeda from exploiting friction between Arabs and Kurds.

With the exception of occasional joint operations and meetings between pesh merga and Iraqi Army officers that occur because of American insistence, no progress has been made in deploying the joint forces in the disputed areas or getting the Kurds and the central government to cooperate on security in a meaningful way, said Sheik Jaffar Sheik Mustafa, who is the Kurdish region’s equivalent of minister of defense.

Mr. Mustafa said the combined forces would be based throughout the north and conduct joint raids and patrols and staff checkpoints. He said the Kurdish authorities had agreed to the idea but opposition was coming from Baghdad and the Arab-led provincial government in Nineveh, which see the arrangement as an infringement on their sovereignty and want Kurdish troops to retreat from the areas they occupy outside their region’s 1991 border.