Syrian rebels are reporting that the US has been increasing the supply of arms to their fighters, particularly in southeast Syria,, with a specific eye on trying to forestall an offensive by “Iran-backed militias” in the area, who are trying to connect a surface supply route from Iraq to Syria.

“Iran-backed” is popular parlance for the rebels, and for the US at times, as a way to say they are Shi’ite militias. The Shi’ite militias are backing the Alawite-dominated Assad government in Syria, and the Shi’ite-dominated Abadi government in neighboring Iraq.

But by and large, they’re the same militias, or at least affiliated ones. The US view of them changes dramatically at the border, however, as inside Iraq they’re treasured allies helping to fight against ISIS and other Sunni Islamists to save the government, and in Syria they’re bitter enemies, trying to fight ISIS and other Sunni Islamists, also to save the government.

This offensive aimed at connecting a land route from Iraq to Syria isn’t just being seen in Syria, either, with a lot of the militia fighters who have been fighting in Mosul recent moving westward, toward the Syrian border, with an eye toward crossing into that area to continue the fight against ISIS after the last major ISIS city in Iraq falls.

Where this is going to leave the US remains to be seen, but while they continue to support a Shi’ite reconquest of the Sunni city of Mosul in Iraq, they appear to be arming up the Sunnis in southeastern Syria to fight many of the exact same Shi’ites as soon as they get across the border, irrespective of the potential harm this does to US relations with Iraq’s government, which has many top militia figures in positions of power.