In its intensifying battle in Iraq against militant group Islamic State, the U.S. appeared to be edging closer towards fighting alongside factions of Turkish origin that the State Department has designated as “terrorist” groups.

In particular the efforts of U.S. President Barack Obama to rescue thousands of members of the Yazidi religious minority community stuck atop a besieged mountaintop in Sinjar appear to be involving an eclectic mix of Kurdish units from Turkey, Syria, Iraq and Iran, among which the Turkish-based Kurdistan Workers' Party, or PKK is considered by the U.S. to be a “terrorist organisation.”

In addition, the Washington Post reported, Washington is arming two other Iraqi Kurdish factions, the PUK and KDP, which are also categorised as “Tier III” terror organisations by the State Department.

In recent days PKK fighters were said to be manning the front line near Kirkuk and “Aided by U.S. airstrikes on Islamic State positions, they also helped take back the key town of Makhmour from the Islamic State.”

While lobbying efforts are concurrently underway in the U.S. to have the PKK de-listed from its terror designation, “that act would require a political will that at present is lacking and risks irking Turkey,” the Post said, leaving open-ended the question about which groups on the Kurdish list the U.S. ought to be covertly arming.