>> These Iraqi Shi'ites paramilitaries are watching for Islamic State hideouts across the frontier in Syria. But they're also keeping a wary eye on US war planes soaring overhead, it's complicated. The fighters are backed b Iran, which the Americans regard as the biggest threat to security in the Middle East.
Reuters John Davison is there.>> Behind me here is the Iraqi Syrian border between the towns of Al-Kahin which is on the Iraqi side here, and Abu Kamal which is on the Syrian side. This is one of the last areas that was recaptured from Islamic State in Iraq about a year ago.
Now Iraqi security officials are worried about a comeback by Islamic State. They say that Islamic State militants, which are gathered across the border in Syria are going to try to infiltrate back into Iraq and set up bases here. The Iraqi military has sent reinforcements to this area, and officers on the ground here say that they are regularly shelling Islamic State positions on the Syrian side of the border, just a few kilometers away.
Iraqi Shia militias are a big part of the reinforcement here and are playing a key role fighting against the Islamic State, including inside Syria. But the growing presence of the Shia militias on Iraq's borders, including groups which are backed Iran, will likely raise tension with the United States.
Which does not want Iran-backed groups to be controlling Iraq's borders.>> The United States is trying to push back Iranian influence in the Middle East. And has imposed sanctions on Iran's oil sector and on the militias it supports. Likewise, many Shi'ites paramilitaries now see the United States as a bigger threats than IS.
As the battle against a mutual foe rumbles on, in this part of the region, Washington and Tehran are setting their sights on each other, raising the risk of new violence.