Iraqi troops and Kurdish Peshmerga fighters were locked in an armed standoff in Kirkuk Province as tensions continue to rise following the holding of an independence referendum by Kurdistan officials last month.
Kurdish commanders said they had rejected an early morning deadline set for October 15 by Baghdad for Peshmerga fighters to relinquish positions they had taken during the fight against Islamic State (IS) extremists.
Both sides are U.S. allies, and Washington has military advisers stationed with the each group in the standoff working to ease tensions, U.S. Defense Secretary Jim Mattis said.
A reporter for the AFP news agency reported seeing armored vehicles bearing the Iraqi national flag posted on the bank of a river outside the oil-rich city of Kirkuk.
Peshmerga fighters were seen behind an embankment reinforced with concrete blocks and flying the Kurdish flag.
A Peshmerga commander said Kurdish fighters had "taken all the necessary measures" and were "ready for a confrontation" if necessary.
An Iraqi army officer told AFP that "our forces are not moving and are now waiting for orders from the general staff."
Kirkuk is just outside the Kurdish autonomous region, but Peshmerga forces in 2014 moved in when Iraqi forces fled in the face of an IS assault. Peshmerga fighters managed to defend Kirkuk's oil fields from the extremists.
Iraqi Prime Minister Haidar al-Abadi has said he was "not going...to make war on our Kurdish citizens."
Nevertheless, thousands of heavily armed Iraqi troops and members of the Popular Mobilization forces, dominated by Iran-backed Shi’ite militias, have massed around Kirkuk.
Mattis told reporters on October 13 that "we are trying to tone everything down and to figure out how we go forward without losing sight of the enemy."
"Everybody stay focused on defeating [Islamic State]. We can't turn on each other right now," he said.
The Iraqi and Kurdish sides have exchanged angry words since Kurds on September 25 voted overwhelmingly for independence in a referendum that Baghdad refused to acknowledge.
The referendum was held in the three provinces of the autonomous Kurdish region, but also in adjacent Kurdish-held areas, including Kirkuk.
Bagdad has rejected any discussion of increasing the area of the autonomous region to surrounding provinces until the independence referendum is annulled.
The United States and other Western powers and the United Nations opposed the Kurdish referendum, expressing concerns it would destabilize Iraq and disrupt the fight against Islamic State.
Neighbors Turkey and Iran, which have large Kurdish minorities, also vehemently opposed the referendum.