BEIRUT (Reuters) - U.S.-backed militias in Syria said they have formed a joint military center with the Iraqi army to protect their common border region after ousting Islamic State militants.

Commanders of the Syrian Democratic Forces (SDF), an alliance of Kurdish and Arab militias, met with Iraqi military leaders on Sunday. They “discussed protecting the Syrian-Iraqi border in the region adjacent to Deir al-Zor province, and how to finally eradicate Daesh mercenaries there,” the SDF said in a statement. Daesh is an Arabic acronym for Islamic State.

“The two sides decided to form a joint coordination center to guarantee the security of the border,” it said.

Last week, the SDF declared victory in its assault in Syria’s Deir al-Zor, which borders Iraq. The offensive focused on seizing territory east of the Euphrates river that bisects the oil-rich province.

The Kurdish-led SDF has been battling for months with the help of jets and special forces from the U.S.-led coalition against Islamic State (IS).

On the other side, Iraqi forces recaptured the last swathes of territory still under Islamic State control along the frontier with Syria on Saturday and secured the western desert. It marked the end of the war against IS, three years after they overran about a third of Iraq’s territory.

Iraqi forces who fought IS came from the army, air force, police, elite counter-terrorism forces as well as Shi’ite and Sunni paramilitaries and Kurdish Peshmerga fighters. They received key air support from the U.S.-led global coalition.

Syrian government forces and their allies, backed by Russian air power, have taken most of the remaining areas of Deir al-Zor province. They are mostly on the western side of the Euphrates, while the SDF is on the eastern bank. Russia and the United States set up a communications channel to reduce the chance of fighting between the two rival campaigns against Islamic State.

Forces arrayed against Islamic State in Iraq and Syria now anticipate a new phase of guerrilla warfare.

Colonel Ryan Dillon, spokesman for the coalition, said Iraqi security forces and the SDF had linked up at their shared stretch of the frontier on Sunday.

“Secure international border protects Iraqis (and) Syrians from remnant Daesh movement into (and) across the region as terrorist fighters/leaders attempt to flee the battlefield,” he wrote on Twitter.